1981 F100 Front Suspension

Have you jacked it up to look at it yet?

Yes Only obvious thing I found was wheel bearings that needed tightning up. That helped a little but there is still lots of room for improvement.

Stupid comments but I'm assuming you've tried the simple things such as inflating tires, alignment, etc.

check the radius arm bushings where they mount to the frame. Bought a truck from my father that had made it through two alignments with the cups pounded out causing the front axle to move forward and back a 1/4"

Thanks, but those have already been replaced. I wonder if it could be the king pins or just the sum of a high mileage front-end.

??? Kingpins???

Ball joints, or inner / outer tie rod ends, maybe, and alignment.