700HP 383 Buildup
a guy i know just a little had a GTX with a 700horsepower tunnelramed 440 (this is no joke this 440 was totaly insane) using brutaly ported iron heads but this was a realy radical streetengine, so ironheads should not be imposible but it will probably cost more to get those heads in shape for all that power than geting some aftermarket heads.