I need to decide what size exhaust system for my Ranchero. It has a 429, Edelbrock 750CFM carb and manifold, CompCams X4270H cam and HEI ignition. I am shopping for headers although those from Crites seem good. I want the exhaust to include an X- or H-pipe. I can choose 2-1/2" or 3" pipes. What is the best choice?