I once had an aftermarket cruise control. It was the type with a module on the console and magnets stuck onto the driveshaft. It worked okay, but when it went bad it was out of warranty and the store said that model wasn't made anymore and no parts existed, "but why don't you buy the new model." No thanks.
 Of course this happened a day before a vacation road trip, and as I drove along I realized a factory system was the way to go. Millions were made, and parts are plentiful, and the controls are in the steering wheel.
 The problem was, how do they work? I could hook up the parts, but what makes it go and how do you check them over? The library had factory manuals that gave some idea, but the best source for fords was a website called http://www.dalidesign.com/hbook/ccmain.html. It is very thorough, and has good basic info that applies to all cruise systems. There's no point for me to repeat what he has there.

Edit: That site disppeared so I linked it back to my saved copy. But here is his new address; http://www.thorssell.net/hbook/ccmain.html

This servo is the main mechanical part of a cruise. It pulls on the throttle when commanded by the electronics. This type is powered by engine vacuum, while some newer ones are all electric. A cable hooks to the engine, so get the right type for your car. Wiring comes out to plug into the brain along with vacuum lines and a rubber cover protects it from the elements.
 On my car it fits inside the fender.

Here it is installed with the fender removed. A bracket must be drilled and screwed to the firewall area, and on my car a hole into the engine compartment had to be enlarged.

 While I was in there I replaced the door hinges. One bolt was broke and the bronze hinge pins were worn out. The outer layers of the firewall was also rusted. It was removed and welders zinc spray was used before a new piece was Migged in. The bolts were replaced with stainless, and the backing plate was ground down for stainless nuts. The drain hose from the sunroof was moved from the inside rocker area where it had caused rust outs.

 An oval hole had to be cut in the firewall for this plug. It has the wiring and a vacuum hose with a valve that connects to the brake pedal. When the brakes are applied the vacuum is dumped from the servo as a safety feature. You don't need it for the cruise to work, but you need some type of hole to feed the electric plug to the inside.
 A plastic tab has to be placed on the brake pedal to push on the valve. I did that but couldn't find the place to screw the valve bracket to the frame and lost patience and welded it in.

 The computer brains are all similiar. Supposedly they react differently for different engine sizes. If yours moves too slow get one from a smaller engine.

 It mounts on a bracket by the pedals. One of the plugs is from the servo and the other from the electrics.

 You can see the white one has 2 orange and 2 green wires. The extra wire is tied into the engine computer.

  Next is the wiring. The rectangular plate bolts onto the column, and must be tilt or non-tilt type. Using the wiring diagrams from the above website labels were put on every wire. There were several 12V and several grounds, which were trimmed down. Aftermarket kits say the 12V should tie into the brake wiring before the switch. I used a standard key on source. However the brake light switch must be used to tell the cruise to pause while braking.

 This is the VSS sensor. It plugs into the speedo hole in the tranny. Like a tiny alternator it sends a signal to the cruise via two wires.
 My stock cable had a knob crimped to the tranny end, and needed to be completely changed.Good thing I bought one with the VSS.
  The wiring was taken from the donor car by ripping out the carpets to get to the plug. It fit right into my car and the wires were soldered to my harness. However one plug was different on the tranny backup light and had to be swapped as well.

 Someone said that all ford hubs interchanged. They are big fat liars. Older hubs have splines and a big nut, while newer ones have two flat spots and a bolt. I found this out Sunday afternoon. It would have been easy enough to swap the column but in the time needed to put the car together and drive to the wreckers I made a conversion.
 The old and new hubs were cut out and cleaned up. Luckily the old one was welded top and bottom. The wheel was filed smooth and the backing plate centered the hub while it was tack welded. It works fine and I like the new wheel a lot.

 I never did any testing. If it works it works. So I went for a drive and turned it on, and it worked! It works much better than any aftermarket one I had. I guess it should. The brain box is much larger and the sensors are better.