383 build help one piece at a time

Build it like EL5DEMON340 said and it will run great. I ran 516 heads on my daily driver for years burning unleaded gas with the 1.6 exhaust valves and never had any cracking seats or abnormal valve wear at all, I never put any lead additive in either. I have that engine in another car now and it still runs good. Go conservative with the cam and use all your stock valvetrain parts and have fun.