Measure from the inside edge of the wheel to the frame. If its off, get adjustable upper control arms, which you prolly should already have, and adjust side to side with those. With those, now you can adjust pinion angle properly. I would recomend also getting 1/4" longer lowers also. Those will allow you to lower you pinion angle without shortening the wheelbase putting the tire into the front of the wheel well. A welded in anti roll bar is the ticket too but now there are bolt in versions that Ive heard alot of good things about, just never used em personally.
Craig