4 Barrel on a stock slant

That formula is accurate telling your the dynamic displacement and ruffly how much air your engine will displace but nothing to do with picking a carb for your engine.

1st I never see anyone measure what vacuum their pulling before even thinking about swapping carb sizes which so easy to do and 2nd we already knows what works for most applications. stock to 350 hp 600-650 cfm 250-500 hp 750 cfm 450-700 hp 850 plus cfm, under 200 hp you could go with a 500 cfm but i'd would be overly concerned about it. Obviously this ain't meant to be set in stone just ballpark.