For what it's worth my 79 p/u had dual pipes out of the manifold that were 2" for about 18-20" long into a single 2.5 pipe to the cat then 2.5 to the muffler then a 2" tailpipe. For some reason they crossed over the pipe after the cat before the muffler. 6cyl trucks had right side tailpipe v8 left. I have always wondered why that was done,after all it cost more to crossover the exhaust. I think that I read on here that Duece Coupe did some expermentaion with pipes. Perhaps he will comment. Jay 6155
