well i dont know what exhaust headers on it, but i do know there is no cat and it goes all the way back to 40 series delta flow flowmasters, and the carb is best for the application as my dad said, and since he built the engine and tuned it himself and i been in it i know he knows what he is doing, im just looking for the best and coldest air flow available, but im thinking of doing a custom job on it, have a 4 inch bolt on cowl induction hood, with a custom air intake tube from the carb to a square air filter that sits about 3-5 inches from the cowl hood so that all the air that breaks over the cowl will hit the filter be at its coldest point and go straight to the carb, all i know is the intake is part of an edelbrock performance package that came with cylinder heads and crankshaft. But i do know the 421 has to be putting out close to 455 hp/520 ft lbs tq, like i said i been in the car once and thats all it took, i have been in many fast cars vette C5, 69 mach 1 with a totally beefed up 351W and none of those have compared to my chevelles power and torque. But thanks and still accepting ideas and suggestions towards air intake.