i have seen many 383 running the e-tec 170 head with air gaps making 470hp and 490 torque.
if higher rpm then look at the e-tec 200's
high cfm and high air speeds is what you want.
on my drag quad i have stock sized valves and ultra high velocity porting and its the best head that i have had done. so i am a firm believer in the high speed and cfm stuff