[Z-linkCobra]

A sway bar or (anti sway bar) and a panhard bar are two totally different things. Sway bar helps stabilize the car side to side. Helps cut down on body roll. Ties the two sides together. A panhard bar locates the rear end in the frame. Keeps it centered and stops it from moving side to side.

A panhard bar will not stop body roll(unless you mount it way low and are turning left and it gets up on the bar...lol) and a sway bar will not keep the rearend located. A fox body mustang uses a triangulated four link. No panhard bar is needed to keep the rear end located. Make sure your bushings aren't worn out. If you have bad bushings on one side that would cause rear steer when you pick up the throttle.

Coil overs or stock springs and shocks?