I was looking up a cat back exhaust system for my car and flowmaster has it listed for american thunder atleast 86-92 is there a major diffrence between 85 and 86 that it wouldnt fit at all or could it be rigged up to fit?

 

Where were the listings you were looking at? In a Summit Catalog or something? Often catalogs dont list their whole inventory to save space. I would call the company you were planning on going through first and making sure they didnt have it for the 85 model before you try rigging something up

 

The early cars have a 4 bolt flat flange connector and the later have a 2 bolt ball style flange. Some 86 cars had the 4 bolt some didn't but all 85's did.