Pick whatever RPM you intend to run as the redline. On the round track cars I figured CFM at 7K-7500. On a stovebolt, most owners get a case of the vapors if the engine gets up to 3K, which is at least 1500 below the point it would start to damage itself. They're too timid to ever approach anything resembling a real redline. 600 CFM is more than enough for any 350 in street trim. The theoretical CFM for a 350 at 7K is 709 CFM. A street engine will seldom, if ever see that speed without floating the valves.
Jerry
