I run a 327 with 10:1 pistons, Comp 280/480 cam, vortec heads, beehive springs, Edlebrock intake, 750, headers and is still shy of 400 hp. Very streetable but a 383 in an El Camino just walked away from me at a light. I am building a 496 BBC and there will be no more loosing! I say build the 383, no replacement for displacement!!!