I can see a stockksh 383 in a heavy car making 300 or so to the tire with that combo. The performer intake will definitely limit the power band in my experience. I would thinf the RPM would be good to at least 6500 on a stock stroke 383. While not 100% apples to apples my 451 with a comp 294h and 1.6's hits a wall at 5800 or so with a performer and stock 1968 bb a body manifolds with the exhaust corked or uncorked.. It acted the same with a performer RPM and headers on the dyno.

My advice would be a 125 or 150hp shot of nitrous. Keep the streetability 95% of the time. Change the timing and warm up that bottle and you are ready to party.