1982 and 1983 exhaust difference

I'm trying to help my uncle find a cat back exhaust system for his 1982 Camaro. The exhaust system right now is completely stock. He's on a tight budget so we are trying to keel the price under $350. I've found that almost all of the cat back systems ar for 1983-1991 Camaro's. What is the difference between the 1982 and 1983 that makes the exhaust systems not fit. I don't know if it matters but the car has an automatic transmission and a 350 engine. Thanks

My Uncle has a 82.

If memory serves me right the exhaust system does not use a large single cross flow muffler, but rather two small standard flow mufflers and a little collector pipe type connector between them.

http://hotrod.com/projectbuild/p105157_image_small.jpg