That's the first I've heard of 3.2 heads being a limiting factor. I've been told that they easily support over 300hp. You might try talking with Bill DiCondini:
BILL DICONDINA
XTREME CYLINDER HEADS
(772)-286-1660
bill@xtremecylinderheads.com
Xtreme Cylinder Heads And Castings
All he does is cylinder heads. He recently redid my heads with all new valves and seats, and some tweaking for less than half what you were quoted.