Victor340 and RPM manifold testing

I get that, Eric explains it in pretty much every video he does :) i was more curious that if someone (Me) is planning a 408 that won't be going over say 6500 (cause i'm a wussy that worries too much) would having 330 over 300 make much difference or does that extra cfm mostly matter to the guys that are running up well over 7k?