the only one I worked on had this factory routing, which works, although the tubes were a bit small. This is a generic internet picture, to show you how it is designed to work. Long, skinny, flat mufflers work best on these cars. And there's a crossover under the engine, even on factory dual exhaust cars.
My '63 BelAir is an X frame, just like that. I ran as shown, but exited in front of the driver's side rear wheel. Mine is a 6 cyl, with duals running side by side, so it's only on one side. Being a wagon with the gas tank in the lr 1/4 panel, & not wanting to put the pipe too close to the air bag, is the reason it's in front of the wheel. If you are running a V8, with coil springs, & it's not a wagon, @squirrel has shown the best way.
The Jalopy Journal
