Most important in my opinion is a C/R up around 10.1 to 10.5 for a street 383, look for some close chamber heads 915's, stealth, even a set of 516, with bowl work and bigger valves would be better than open chamber heads, also don't over do the cam, 220 to 230 at.050 for good all around low to mid range. 230 to 240 for hot street. On my worn out stock 68 383 hp motor with factory flat top, i replaced the 906 with 915's, and replaced the cam with a vodoo 220/226 475/494 112cl and was very very pleased with the power and performance, its about 9.8 cr with .040 fel pros with a quench of around .040 to .050.