The Pitman arm is considered a non-wear item. It only has 2 holes and no moving (swivel) parts. Main reason to replace it would be because it was bent from impact damage. That's why nobody shows it in their parts catalog, they hardly ever go bad. The holes could get wallowed out or elongated if the nuts on the center link or gear box were left loose, I suppose, but I've never seen that happen.
Check the usual culprits for play: Idler arm, outer tie rods, center link, ball joints, wheel bearings, inner tie rods, A-frame bushings and of course gear box. By the way, there are TWO adjustments on the gear box to do it correctly.
You know, Gyrheads and Sons makes a complete Moog front end rebuild kit for around $310. Parts only. HTH.