That'll be a BIG upgrade from 906s. Engine Masters did a test on a 440 with Trick Flow 240 vs 270 heads and the bigger heads had gains pretty much everywhere. I do hear P-V clearance can be tricky with factory high-comp 383 pistons though if they don't have valve reliefs. Quite a big intake port to feed 383 cubes but if the rest of the combo is right it'll be a real screamer.
