early A body exhaust EXPERTS!

The exhaust places I have chked pretty much all said to put an X or H pipe either one as far back as is reasonable for trans access and driveline clearance.
As I looked into it, there were a lot of systems that had the X type just behind the trans.
The main thing an X or H do is to dampen the exhaust noise by breaking up the sonic reverberation that builds in a single pipe, so it really does not matter where they are in the system.