....I read something in Hot Rod Magazine awhile back where they used Brodix aluminum -8 Heads on a blown motor {Chev. small block}. They said that these heads had 1.80 exhaust valves and that this was the major contributor to the high HP readings that this motor produced.... so you might check out these heads. But then, as someone mentioned eariler, your lack of large free flowing exhaust headers arn't helping things at all...... Bill