i built a 383 for my 69 roadrunner, broke it in, ran it one time.. and it just wasnt fast enough, so i picked up a 440 to build a 512 stroker with. i recently picked up a set of the stealth heads from 440 source and theyre ported to flow 330-340 cfm and have 2.14/1.81 valves, great heads! BUT...