in order to really get that thing breathing healthy I would look to change the intake and go with a Holey carb. The stock intake is designed for what they call peanut port heads. Its a very small oval port. I would make sure it will work with your heads. You would be better off with 454 or 502 mag intake or even a open plenum. adding a set of roller rockers isn't a bad idea either. also changing the cast iron risers on the exhaust to stainless would be helpful with out having to spending thousands of $$$ on new manifolds. finding these parts on this board should be easy.