There are several sites that talk about converting to Electronic Fuel Injection, and this is another one.
 For years I had no great desire to convert. I never thought I would own my 'fox body' Mustang this long, but I had rebuilt the engine and wanted to get my equity out of it. I had gotten a carb to perform pretty well, and I also thought that Ford EFI intakes were kind of ugly. ( I think GM has some good looking manifolds, but Ford just doesn't get it, and the aftermarket ford isn't much better. )
 The engine is an old style 302 with ported heads, flat tops, and a Performer 289 intake. When the engine was rebuilt the hot cam was replaced by a 'torquer' type. This purposely limited the revs in exchange for more mid-range.

Various aftermarket carbs had been used, but now a '70s Motorcraft was on top.This carb is a bit of a frankenstein. Some parts resemble a carter, a quadrajet, or thermoquad. The accelerator pump is held UP by the linkage and a spring pushes it down. The secondaries have a piston that pushes against the gas, so they are hydraulically operated. It was the best all around carb I ever had with far better mileage than anything else.

 However, the car still had hot start and cold stalling problems, so fuel injection was in my mind. A factory carb type system seemed simpler, but it turned out to have just as many sensors and wiring as the much better multi-point sequential type.
One day I was at the wreckers and saw a complete t-bird with efi. I decided this one would be the start of the swap. However as winter was coming I decided to collect parts until spring and do the conversion then. Also, at the time I only knew the basics of fuel injection and never tried to learn more, so some reading on the internet was needed. I wanted to understand EFI thoroughly before it was put in the car.
 The first day all the mechanical bits were removed, such as manifolds, injectors, and throttle. I also removed the computer and followed the wiring out to every device that was hooked to the computer. It is a lot of wiring compared to a carb setup, and took several hours. There was a big duffle bag full of stuff, and at the checkout the guy called it an intake and charged $12.00 for everything!
  It was quite a big job cleaning it all up. A pressure wash didn't help much so everything was sprayed with oven cleaner and scrubbed. Finally the manifold was sandblasted with my el cheapo pail of sand blaster. I wanted to have a bare aluminium manifold but the factory coating was too tough. So it was smoothed out and epoxied and spraygunned with some generic metallic silver from the auto body supply, and it looks damn nice. To match the look the engine color scheme went from blue to black and silver.
 The net had several sites with the newer Mass Air systems, but I had an earlier Speed Density unit. Conversions are possible but I decided to keep it and maybe convert later. The first goal was to get it running. I found out that a mustang DA1 computer was the one to have for SD and the harness had to match its' plugs. I also wanted it to be 'stand alone' and leave the stock harness in place.
  A local ford dealer had a room full of old manuals. I searched them, found the right schematics, took them to the office, photocopied them myself, and then some assistant shop foreman charged me a dollar a page 'for his trouble'. (and I think he was half drunk too.)
Anyways, there were 5 11x 17 sheets along with an enlargement of the computer area. Now I began to understand how it all went together. ( these early drawings showed a knock sensor, which the 5.0 never had! ) I can't scan such a large drawing and can't find any speed density scans on the net, which is why I went to the dealer in the first place. However here is a colorful mass air diagram.
  The drawing of the computer pins wasn't very clear so I made notes and later cleaned it up. Only a few pins in my harness had to be changed. Wires were also added to convert to mass air later on, as these pin locations are empty on a speed density. Here is the drawing.
 A Saturday evening was spent down by the washer with the wiring harness. Every wire was checked at the EEC pins, and from every sensor backwards, and tagged. In this way the wiring was cleaned up, trimmed to length, and consolidated into a stand alone harness with 2 positives (for EFI and fuel pump relays) and 2 grounds (for EFI ground and TFI anti-static). It looks like a lot of wire at first.
 The harness had several wires left over, which were cut short and left in the firewall plug for any future use. I also recommend hooking up the harness to 12 volts beforehand and testing each plug. It's easier than fixing it in the car. Some of the wiring was faulty and it was a pain to fix. ( I had hooked pin 60 to O2 heater ground, but not to any chassis ground.) Also ground everything to everything under the hood, and check old ground wires.
  My engine has the old 302 firing order, so the injector harness had to be changed. This could be done at the EEC pins but I did it at the two 10 pin plug-ins, and cut off the plugs at the same time.
The 2 firing orders are 302  1 5 4 2 6 3 7 8 so only four need to be switched.
                                  5.0  1 3 7 2 6 5 4 8

[ UPDATED- There is a problem with this re-ordering. I was having a problem with the engine running leaner and leaner everyday. I double-checked every sensor and they were okay. If I purged the computer it ran good again for a while. Then I tried unplugging the O2s and it ran better than ever.
  Soon after I was informed on a forum that the computer can adjust each injector bank seperately, based on O2s. If it reads lean on the left, it richens up those injectors, but now some of those injectors are on the right! So the right gets rich so the EEC leans it out, but some of those injectors are now on the left! So the engine gets leaner and leaner.
Exactly what I could have figured out if I had thought better. I wonder if I can 'siamese' the O2s. More on the TUNING page.]

 Injectors are rated by how much they flow per hour, and flow is related to horsepower. 1980s T-birds and LTDs have 14 lb. gray tops, while mustangs and trucks have 19 lb. orange tops. I found a 4.6 ltd and they have orangetops. The car was not a taxi and the injectors looked new. I also took the fuel pressure regulator, because it was chromed, and the Mass Air Meter, for the future conversion.
 The stock lower intake is the same on most 5.0, and the number 1 and 5 ports have a 'dogleg' shape that slows the flow. The bad areas were ground out as much as possible and the ports matched to the heads. The upper intake had the throat cut bigger with standard wood router bits. They cut aluminium and brass quite well.
The PCV has a little basket under it filled with steel wool. This was totally clogged and had to be dug out and replaced with a piece of stainless steel scouring pad. After this the intake was torqued down and the fuel injectors and lines were added.
 The stock 50mm throttle body was bored out on my lathe to 58mm using a plate from a V6 Aerostar and given a funnel mouth shape. See? ( strange that a 3.0 L has a bigger bore than some 5.0.) A stock Mustang has a 60mm or bigger, and aftermarket units are any size you need to brag about.
  I bought a roll of metal fuel line at Napa, but when I realized all the bends it needed I went back to the wreckers. I found a stripped out 87 on stands with only the fuel lines and a DA1 computer. The 2 lines came out in one piece but had to be cut in half to get them home. At the front the brake line bracket had to be lowered to fit the lines above it. The old bolt hole can be seen under the lines.
  A propane powered half ton had a 'like new' external fuel pump so I decided to go with that. Besides, around here the tanks get punctured by the self serve wreckers so a good tank would be hard to find. The pump was mounted on the panhard bar support using a bracket from a 280ZX. A filter protects the pump and also acts as a small fuel reservoir, providing the pump with a few seconds of gas if the tank sloshes. I can go past Empty with no problems. You can see that the panhard has been throught a few winters.
 The main fuel filter needed some thinking to mate with the external pump and the stock lines. I collected several examples with the same size outlets. The Nissan is the same as the Ford except it's set up for rubber hoses. The Subaru was choosen as it allowed the most clearance with the exhaust. It was mounted in a mustang factory filter holder that I bolted to the floor of the hatchback.
 The firewall had a round hole that needed to be oval to fit the EEC connector. I used a dremel with a cutoff disc to get the basic shape and then rounded it. The rubber plug had another hole and a slot cut in it to get the old wiring back into place.
The wiring was laid out and all the sensors were added.
  A diode style starter relay was installed, along with a GM auxillary stud. As the old harness was kept the solenoid stayed on the passenger side. 2 circuit breakers were added for the efi and fuel pump. I may rewire these for a small fuse panel which would make it easier to purge the computer.
 A rigged up air cleaner was made from GM parts and a can of corn to get everything running. Later the battery was moved to the drivers side and a factory air cleaner was installed. I chiseled off the mounting plate from a cougar and cut the fender to hold the rubber mounts.
 A car that came with EFI has a pocket for the computer. Mine didn't, but the EEC barely fit between the heater and the passenger kick panel. A mounting plate was made for the stock holder. The 2 relays were Ford Bosch types that an auto store was selling surplus for $1.50 each. The wire for the pump was placed in the holders for the rear brake line, which was moved years before. The fat red wire was from someones stereo sytem.
 A few months later a proper pocket was created to protect the computer and so the kick panel could be replaced. With extra wiring the EEC could have been moved under the passenger seat, but I didn't have any, and was sick of splicing. After the fender was removed, the area was marked out to copy a stock pocket. Then it was cut out using an abrasive blade in a circular saw. Any hardware store has them. The door got very wobbly and was removed, which was handy anyway. The bushings were replaced as a 'might as well'.
 Be careful not to cut through any stock wiring. I knicked 2 and had to splice them. Here's the wiring. It comes down, plugs together, and goes back up. I untangled it and stuffed up beside the glovebox. Notice that the heater has a gap behind it for the efi wires.
 Here is the metal tacked together. Plate was used on the bottom half as it ties into the door hinge. The rest is sheet stock from the hardware with flanges made for easier welding. It was then cleaned and undercoated. The sunroof drain moved to the antenna hole and a new hole was made for the antenna wire. Inside, the same EEC plate was altered and a piece of wood spaced it away from the door bolts.
 The TFI distributor had to be altered because it has a steel gear, which would destroy my old style camshaft. The old duraspark dist. has a cast iron gear with a smaller hole. Some say drill it out, but I found that an older 351 has the proper gear to use. The only problem is getting it off without damage. ( Why does ford put them on so tight? GMs fall off after the roll pin is removed.) I bought an old dist., cut the shaft, heated the gear, and tapped it off. ( I also put a grease fitting in the TFI distributor)
 Finally, it was all together. Mainly. Despite knowing it should work, I wondered if it would. I hotwired the EEC and cycled the fuel pump several times, turned the starter, and it started. Yippee!
 So, after adjusting the Timing and Throttle Position Sensor I babied it down to the car wash. As I left I stepped on the gas as usual and almost did a doughnut! The pedal had become very sensitive. The change was dramatic, and fun.
 The next few months there were a few fine tuning problems to be solved, but most were solved by testing all the sensors and understanding what they were doing. They all started out as junkyard parts after all. However, some of the quirks seem to be part of the EEC programming, and people with Mass Air seem to have them too. I am currently trying to fool it by altering the inputs.
Some people say that EFI does not increase power. With my combo that was wrong. Power and torque are way up, and the clutch can't handle it. The engine revs quicker and higher. Temperatures are lower and more stable. Gas mileage in town is also up 35 to 40 percent! I haven't used a whole tank on the highway yet, but am expecting good gains. The total cost to get it running was a low $130.00!
 Overall the car is better to drive. Somehow, it also handles better now. Perhaps it's the throttle response or the fact that the carb doesn't starve in turns. During the install many other problems were found such as loose door hinges and rust holes that let noise in. The insulation under the back seat was never installed at the factory, and the radio is clearer with the built in suppressors in the harness.

Should you do it? Yes! But there sure is a lot of wires at first.