[25stevem]

Since both heads have the same valve size and plenty of meat for porting, the limit in terms of the D port head is the area at the Exh flange for bolting up a header bigger then 1 7/8" .to 2".

Since there Aluminum though you could weld and make them the port area needed at the flange to better match what that nice big valve can do.
Doing this you could get round port headers to maybe work, but I don't think it's necessary.


That being said, SBCs with there 1.60" Exh valve make 1100 hp with there Exh port size they can go to when ported, so I don't think if your shooting for 1100 hp with a aftermarket D port head that you will be disappointed.