383 question

Most importantly welcome to the site. Where you're sitting right know I'd guess 400HP, do you know what the CR is, hopefully at least 9.5 with a zero'd deck. Improvments, your carb is to small especially with an aftermarket intake and headers, mine loved a 750 DP'r. The performer RPM is a better all round manifold but you'll have to get pretty imagineative with the air filter if you don't have a hood scoop. Done properly (bigger carb) with the cam you're running (which I consider mild) and intake and exhaust fine tuning 450HP is easy and 500HP is a good target without going nuts on the compression (imo 10 to 1 best) and an M1 intake and better cam. Oh yea, 383's loved to rev., big bore x short stroke and 6000 with stamped steel rockes is about max., add roller rockers and add 500RPM.