I do my own alignments, I'll tell you right now if you're lifted more than 2 inches you're caster will never be at "spec". My front is sitting at about 3 inches and I can't even get close to spec. But as stated before, it will not wear your tires any different. As long as they have you set to -.6 on both sides you would never know the difference. Once you get into being, we'll say, -.6 on one side and .6 on the other side your truck will start pulling to the side with the least amount of negative caster, if you can let go of the wheel and it still goes straight your caster is set as close as it's gonna get. As long as your toe and camber are set to spec you're tires wont wear unevenely.

The escentric bolts on the lower control arm is what sets the caster and camber and the tie rod ends is what sets your toe. The upper control arm is basically along for the ride. I just wanted to clarify that from a previous post.