Need help finding exhaust

I've just become the proud owner of a 1979 5.0 Ghia coupe. This is my first V8 mustang I've had in a very long time and loving every second I get to spend in the drivers seat. I've been searching for a hour now and I can't find any answers to my questions. I want to replace the old single pipe exhaust that's under the car now. I've gone to numerous websites and the farthest back that anybody goes is to 83. My questions are: 1.)What are the differences between the early (83-85) 5.0 exhaust systems and the later (86-93) systems? 2.)Who makes a duel exhaust system that will fit my car?