For a 383 shooting for 600HP, better go bigger on the heads. 210's will be better. AFR heads are great. There are others as well. Look at DrJ's Airwolf heads. Better flow for a little less $$ with full CNC.
I saw a magazine article where Joe Sherman made 600Hp on a 383 with AFR 195's but he's the master. I'm a hair shy of 600HP NA with 220's that flow better than the AFRs and a decent cam (250@50 and 600lift.)
For the best mix of economy and power, shell out for an EFI set up.
Or just add a 100HP shot of nitrous and be done with it.