Originally Posted by the82elco
i was going to put it on a mild built sbc 350 bore 40 over
Holley's Interactive Carb Selector
recommends a 600 to 650 CFM w/ vac secondaries for a "mildly modified" 350 with a max RPM of 6,000 in a vehicle weighing more than 3100 lbs ... etc.
Here' an actual CFM calculator
which accepts some variables (like Volumetric Efficiency).