Try rotating your tires... it may not solve the problem - but if it changes things then that points to it being a tire problem.

Also, as far as testing for bad ball joints, centerlinks etc, you usually test them by shaking 'em. For the ball joints, jack up the truck to get the front wheels off the ground, grab the tire on the top and the bottom and give it a good shake. If it feels like the wheel is rocking back and forth at all then something is worn out.

Similarly, get under the front of the truck and give the centerlink a good shake and see if the little ball joints on either end have any play in them.