Wow, you actually believe they ran those mufflers on the race cars. If you gain power with a X pipe if you would put a couple in a row. It would really fly then. How many X's can you fit on an A
Stop bein such an ***. Both my Roadrunners had H pipes, but who knows, it may be that Ma used H instead of X because it's cheaper to build.
So far as running pipes at the drags, I guess you never heard of pure stock. The factory was certainly aware of exhaust restrictions, even if "some of us" were not.