I would address the possibility of the steering box being bad for last, since it is the most time consuming task if a rebuild is necessary. They can be rebuilt. No need to buy a replacement usually.
You need to check all of the other steering components first.
King pins.
Wheel bearings.
Tierod ends.
Pitman arm-to-steering arm joint(at left spindle).
Leaf spring shackle pins.
Old bias ply tires will also cause auto-tracking in minor ruts in the road
Carl
Last edited by 52Carl; 01/22/2015 11:46 PM.