As said, have someone sit in the truck and work the wheel back and forth, you'll see what moves. Lower balljoints/control arms or steering center link could be the culprit. Also, the frame horns on these trucks move ALOT. I rebuilt my entire front end when I bought my truck and still had some play. Had my dad move the wheel while I was underneath and the whole front crossmember (where the brake prop valve is) and front of the frame horns were twisting. '81-up went to a front crossmember with huge holes cut out for lightness, but it's much less stiff