Ported 452 or Edelbrock RPM

So the big question here is what cc did the heads start out as. If they were the 84cc heads to begin with, they would have been milled at least .060" to get to 74cc. This will reduce your piston to valve clearance the same amount, at least .060".

The compression is probably not a problem as the combustion chamber shape will help and the cam is big enough to reduce the cylinder pressure to pump gas levels.

The RPM head should use the same ARP head bolts as the stock iron head.

The pushrods might work as the 452 heads must have been milled to get down to 84cc.

The compression bump and the head flow increase should make a noticeable difference. You can't race flowbenches so..........without a flow sheet from the same flowbench for both different heads it's hard to say for sure.

The rocker arms should switch right over but you may have to space the bolts to the rockers differently to center them back over the valves.