[Bill Harris]

In the engine spec for the 68 Ford the entry for the 302/320 Comet & Cougar it says you can use a Holley carb and there are some Ford P/N's. There is also a reference to note 15. If you look at note 15 in the Carb Specs it says:
15 - 1563x1563/1250x1313

What that means is that the allowable carb has a primary and secondary throttle bore of 1.563" (which is 1 9/16"). The primary venturi size is 1.250" (1 1/4") and the secondary venturi is 1.313" (1 5/16").

So any Holley carb that has those throttle bores and venturi sizes, and is the correct model (4150 in this case) and has the proper fuel bowls (center pivot "cathedral" type in this case) and has the choke horn and choke blade in place (can be wired open), is ligit.

Essentially, those throttle bore and venturi sizes are used on most Holley 600 CFM carbs. There are some variations on the booster venturi's on various carbs, but NHRA doesn't care about those. As long as it is the correct model, throttle bore and venturi size, and has the choke junk, you can use it.

You could use an 1850 body, convert the secondary metering plate to a metering body (4160 to 4150 conversion) and use center pivot bowls and it would be ligit.

If you have FoMoCo 0.030 pistons for that engine then they are legal. Don't have to be on any list except for FoMoCo's. Those are cast pistons aren't they? Not so sure you want to use them in a S/S engine. Your likely going to have to cut some pretty significant valve clearances on them for a big cam. Doesn't sound very durable.