There are a whole lot of variables that you would have to define, but here's a basic rule of thumb from a cylinder head perspective:
HP/2.25 = Peak CFM per runner on a Stock/Super Stock style engine. A decent engine in this world will make 2.25hp/cfm of head flow. Really efficient engines surpass it, and lesser refined motors may be a little lower. But this should get you in the ballpark.
So if you want enough head to support 650hp, you'll need around 285-290cfm of peak flow to get you there pretty easily. The big thing you need to figure out is at what peak RPM you want to make this 650hp
