In making my decision on a carb, I also looked at the total ( WOT ) cfm of the intake as well as the carb. It goes along right with what Frank said, it is a balance determined by the performance you build your engine for, higher rpm requires higher cfm, but you loose performance/ drivability at lower rpm. If you have stock engine and want to add performance enhancers ( 2 barrel, headers, ignition). You still are probably going to never hit 5k on the tax, going with a more conservative carb will give you better drivability from idle to say 4k. If your carb is over the cfm of your intake, you are in the too much carb range. I’m not sure of the cfm on a 38, but I know the 34 is better matched to a stock head, and my large log modified 2 barrel head, the 34 was quite a bit to small ( 50 to 75 cfm if I remember correctly
) I don’t know what the cfm is on a 38 either. As of now, I am planning on a Holley 2 bbl for the modified head engine pretty much because I am more familiar with rebuilding and tuning Holleys. And it matches the total cfm pretty close and my build allows for pushing 6k (long story but not my first choice
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