I've noticed searching on the forum that some people use either the moog 824 or the 844, and what do you guys mean about bushings?

The upper balljoint is not mounted directly to the spindle in the truck. The upper balljoint hole in the spindle is way bigger than it needs to be, and then they install a sleeve or bushing to make it fit. This bushing is eccentric or egg shaped. The alignment guy spins this eccentric bushing around, and it moves the location of the upper balljoint, the lower balljoint is fixed tightly in the spindle and will not move. So this is how they tilt the top of the tire in and out so it's plumb looking at it from the front of the truck (camber) and is also how they tilt the spindle back at the top in relation to the bottom balljoint (caster). They have to adjust both caster and camber with the one eccentric and try to get them both in tolerance.

If you lift the suspension on these trucks in the front, the suspension swings in a arc, and the front tires will be tucked in at the bottom. There is only a limited amount of adjustment in the eccentric bushing, lift it too far and you can't get it back in alignment. That is why they have lift kits with drop brackets to bring everything down together and try to keep the wheel straight.