X, J, or 308?
i have heard x or j will support 400 hp,but don't have any first hand info...
YES! it will.
In lay man's terms, the amount of HP a head can / or will produce is cfm X's 2 for most builds. Not all builds. AKA some really serious HP hunting engines. It is possible to exceed the basic formula.
A stock head flows approx. 200 cfm. X's 2 is 400 (HP)
The less cfm flow, the more cam, compression it will need.
MoPar Muscle has a few articles on this.
I remember a chick did a 360 with Edelbrock and RPM intake, 750 carb IIRC and wacked out 400 HP. The thing behind it all was the cam was barely lifting mid 400's. This is NOT using the head at all and the head doesn't flow all that much at that lift.
In another example, the (Stock) Magnum head (1.92-1.60 valves) was used with a 280/.480 comp cam. Though the 1.6 rocker moved the lift up to .512, the head could still handle that lift. The engine made over 400 HP and the displacement was a mere 318.