i gotta a 406ci with dart iron eagle cast heads 2.02's....flat tappet cam..5.20 lift range.....vic jr intake...750 Holley HP
its also 10:1 motor with flat Tops
It made right at 460hp on the dyno with almost same amount of TQ.
i know the 383's are a little different set up..but i would say you should be in the 420/430 range .....
i think it would be quicker if you took that Tunnel ram off and went with a good intake and Good single carb.