Regarding running the exhaust out to the bumper.
- It is possible, you just have to get crafty.
Here is a pic of a nice 71 Demon equipped with the streetlynx rear suspension, a Dana 60, and exhaust to the bumper.
The exhaust fits very nicely in the space vacated by the leaf springs.
http://www.gforcedesignconcepts.com/gallery/DEMON?page=1