Carb cfm selection can be found on the Holley site. Carb brand is up to yourself. I choose Holley and this site revolves around that choice. I am not going to get into the carb itself just how to adjust it. You will find with carb adjusting too much info is a bad thing. Mechanical secondaries have less adjustment and less chance of failure.

Floats
    Float adjustment is very crucial to the proper working of all the metering circuits. Remove screw cover on side of float bowl. When float is properly adjusted gas will dribble out of hole. Loosen lock screw on top of float bowl. Turn float adjusting nut clockwise to lower fuel level. Counter-clockwise to raise.
Primary idle screws
    These can be set by vacuum or by idle. You are looking for optimum lean idle roll. Personally I set them by ear. I found that 1 3/4 turn works well.
Power valve
    Holley recommends using a power valve size equal to half the manifold vacuum. Haynes suggests a power valve 1 1/2" lower than vacuum. Economically, use the one the carb comes with and adjust around it, if it is at least 1 1/2" below vacuum.
Helpful hints
    Do not try to adjust the secondaries first. Do it in stages. Primaries then Secondaries. If you have not adjusted the primaries. Stomping the car to the floor is wasting time and gas. Most people make the mistake of thinking that jetting down results in shooter size dropping as well. If you use Holley's power valve suggestion you will probaly be jetted high and have low shooter size. Haynes way will probably set you with lower jetting and higher shooter size. I opted for a higher power valve, low jetting, and large shooters. Since my street car runs a Holley too, my theory is: the car runs mostly on the jets so it should save on fuel.
Shooters
    Trial and error. It can get expensive but this is how it's done. If the car has more than a one second pause, change shooter 3 sizes up or down. If less than a one second pause adjust one size up or down.
Jetting
    Jetting is accomplished by examination of the plugs. You want an earthy dirt like color. White or beige indicates too small of jets. Black indicates too big of a jet. After getting jetting straightened out. You may get a pause back in acceleration and have to resize shooter.
Secondaries
    The secondaries are adjusted basically the same way. The problem is you cannot keep the four barrels open long enough to change plug color. If you have black smoke coming out of your exhaust you are jetted too high. If you want to try to get plug color from the four barrels. Open the four barrels as long as you can and shut the power off to the ignition (see "Wiring Section"). Do not turn off the key and lock the steering. Coast to a stop and pull the plug. If you have a pause on launch the shooter size is wrong and is adjusted the same way as the primaries.