Higher CFM will improve the top end. Lower CFM will improve your low RPM band. For a street driver you want to keep the CFM on the low CFM side of things. Too big will be nothing to brag about for street applications.
There are guys out there with 350 cu.in. small blocks and 750 CFM carbs that I can beat with a 283 cu.in. and a 350 CFM 2 barrel carb.
