Help! Dog Tracking!!
The thrust angle is a non adjustable angle on a Mopar. It is a comparison of the vehicle centerline to the rear axle centerline as viewed from the top of the car. The only way to adjust it would be to move the spring perches. You might can make some very small adjustments by loosening the rear axle U blots and trying to move the rear axle, but it will probably not be much at all. The only adjustment on the rear regarding shims is the pinion angle, not the thrust angle. The only other way would be to try to compensate for the incorrect thrust angle with the front end alignment....but again, since the thrust angle is a measuerment regarding the rear axle relationship, you're sorta putting a bandaid on the problem. Best bet is to get it on the rack and CONFIRM what the problem really is and go from there. Because all this batting it around online is guesswork at best.
I will add this.....you MIGHT could get a little adjustment by making some shims to put between the front spring hanger and the hanger mount, but this is really not an accepted method. IF the thrust angle is out and all of the bushings are in good ahape and intact, I would be lookinf for possible previous crach damage regarding the frame rails. BUt of course, as I said, ALL of this is guesswork until it sees an alignment rack.
Here is a shim kit:
http://www.jegs.com/i/Hotchkis/515/3003/10002/-1?parentProductId=1348322