Back in the day, EVERYONE knew that a 383 would run much better with the carb from a 440 on top of it. I imagine the carb to use was the one from the higher performance 440. Shoot, that carb was even the right one for 340s!

AFBs and AVSs have a secondary that opens on demand so the carb is only as big as the engine needs. I ran a 600 Holley for several years on my low po 318 with decent mileage and driveability. It ran better with a later 570 Street Avenger but I attribute that to a better fuel curve.

The tune on the carb is more important than the cfm. That's one more reason that fuel injection is so good, at least the ones that use an O2 sensor.

R.