Non mandrel bent exhaust?
The problem here is the answer isn't exactly in stone due to the pipe bends. Where they are, how crushed they are. The big tube is a problem no matter what and/or where the bends narrows. It's still a 3 inch sewer pipe.
A simple semi temp soultion is a Jegs or Summit exhaust. Very cheap, but a true dual. I have a Jegs system on my Dusters teen. You can add an X in it later on. The true dual isn't as powerful as a X system, but will allow for lots-o-power.
Click here, it's in there somewhere;
http://www.forabodiesonly.com/mopar/showthread.php?t=10508&page=1&pp=20