Where?
You need to take some measurements- so you know if it's the suspension, or the body on the frame. Not sure where the best points for reference are. I would think that at the rear, the center of the bushing where the lower control arm attaches to the body would be good, and at the front, maybe the center of the pivot for the lower A arm. If those are the same on both sides, then the suspension is "even", and the body to frame mounting must be the problem. Could be something as simple as having a rear spring "twisted". I think that if they aren't turned with the pig-tail in the right location, (between holes in the spring seat?), that can affect ride height. There is a sketch in the service manual showing the spring orientation.