Newbie rear susp question

[goa484]

Hi, I just got into doing some handling mods on my gto. I have adjustable upper and lower control arms on the rear that seem to be equal in length but I have the passenger tire about 3/4" closer to the quarter panel than the drivers side. Could just be a body issue but I was wondering what techniques you guys use to make sure that the rear is centered and square with the chassis. I also seem to have a slight left pull but only under moderate to heavy acceleration.
Thanks!