I don't think the pitman arm will help. First check all the steering linkage, tie rod ends, ball joints, steering gear and wheel bearings for play. Fix these first. If you still have the problem it could be the caster is off. The cure could be as simple as using longer lower control arms.
2000 XJ Limited, 4.5 Rusty's All spring lift; 265/75/16 BFG KM2's; 4.0, aw4, 242.
2001 XJ Sport, 4.5 Rusty's lift, 32x1150x15 Hankook Dynapro MT's. 4.0, aw4, 231, 8.25 rear with power trax locker.
08 f 150 2.5 lift, 33's, arb.