Finally got an old pickup truck!

could not find my notes yet but looking at napa on line, the 3000/3600 gvw are same. they are different from 3800/4000 gvw. basically depends on what brake size-12x2.5 or 12x3.0. same with wheel brgs. so if he has drum brakes on front now, he could take spindles and change to disc brakes and cross over bearing numbers to get right stuff. also,as you said ball joints show different also,depending on gvw.