Hey I'm new, had afew ?? I just put a 86' 302 in my 70 f100 and I had to convert it to a carburetor. I ordered a holly 2 barrel 500 cfms, was trying to make sure I got the right one if ne1 got any Suggestions.
IMO - 500 cfm is not too big for a 302. How it gets there is not ideal though in two barrel form. I agree with DanH for a stock engine redlining at 5,500 RPM or so.
The 500 cfm has bigger venturis that are not ideal for low RPM usage, and has the big 50 cc accelerator pump, and is probably jetted pretty high.
I put a 390 cfm 4 barrel (8007 model) holley on a mild performance 302, with an AOD and 4.11 gears in my '71 F100 and got 17 MPG when I kept my foot out of it.
I'll agree that the smaller 4 bbl carb would be a better choice for a stock 302. The 500 CFM 2 bbl.'s are better off on a built motor that has carb restrictions and such for some kind class racing and not really intended for casual street use. A small 4 bbl with vacuum secondaries would be better even if you don't have a 4 bbl intake. If that is the case you can run a carb adapter from 4 to 2 and use your stock intake if you have room of course. If not I'd pick up a used aluminum 4 bbl manifold off the internet (check here as well) and go that route before using a 500 2 bbl you're talking about.