For an 84? I think your best bet is to take it to a local muffler shop and have them bend you one from 2.5" tubing. I had one custom made that way in about an hour for $300, including muffler. With the turbo, though, you don't even need a muffler unless your State/Province requires one. Just run the pipe to the rear edge of the rear bumper.
Regards, Stan