It sounds like you're running too much air pressure in the rear for running empty. I concur on the alignment check. I would also check for bad ball joints or a loose tie rod end in addition to the track bar. If all else fails and you can't find any loose parts, a good steering stabilizer can dampen the motion that causes death wobble, but if you have loose parts, it's far superior to fix that rather than try to hide it with a shock.
I am quite surprised to hear of death wobble on a truck with factory sized tires. Something must be badly worn (which is a good thing, because that means it'll be fixed once that is replaced).