Yup, all of the above. My had it bad, on the way home from buying I found this out.
re-did the king pins, helped but no fix
shocks, helped but no fix
tires, helped but no fix
spring bushings (but not the trac bar), helped a lot but didn't fix it.
tightened the wheel bearings tighter, corrected the problem.
Things to do:
caster shims and trac bar bushings, maybe a shackle reverse if I can figure out how to do it without lifting it.
All of this has been mentioned above, but I'll go with ball joints and bearings a little loose.
There is also a couple companies making ball joints with no nylon race. The nylon race is probably being beat with the larger tires and 7.3 weight on top of it, this might be adding to lots of extra play. And did the shop do it right when it was rebuilt? I'd hope so but it's very hard to know unless you do it, really hate to say that.