Your butt may be draggin! But like Ed said butt sag is when the rear fiberglass drops leaving a 1/2" or so gap at the top back of doors where it meets the rear of body.
Aftermarket adjustable rear spring plates allow you to raise or lower one or both sides. Or pull the torsion bars and reindex them.
An easier alternative is to lower the front of car to make it lower and match the lower rear. Easy if you have torsion spring adjusters in the center of the beam --- or add dropped spindles if a 2" drop is what you are looking for.
