here is my suggestion. Sell your running 502mag for 4-6k. Then pick up a good used 500efi or 525efi for 10-15k. You will be in it for 5-9k plus labor. You will gain 75-100 hp, won't grenade your drive and will have the resale value and reliability of factory power . Good luck mike

If your looking for an exhaust upgrade I have a set of stellings (green) 89 bbc 454 502 572 should bolt right up they came off of a 454 running 550hp.