Tommy has given you some good advice. I've never been able to make one side caster be different from the other side in these trucks. That axle is not easy to twist and my experience is using different caster shims just causes the spring to twist more on the side with the higher degree shim once everything is tightened.

Please make certain your steering is aligned so that when your steering wheel is pointing straight ahead your sector gear (inside the steering box) is right in the center of its travel. Actually it should be smack in the center of your ball nut so that the center tooth of the sector gear (there are 5 teeth and the center tooth is number 3) is in the center (which is the high spot for it). This will be the tightest spot...where the number 3 tooth contacts the ball nut. As you turn to the left or right the relationship between those two parts becomes looser. It is very important for the tight spot to correspond with the "driving straight ahead" steering wheel position.

With the 1/2 ton trucks I normally use 3 degrees positive shims. Makes driving in town a bit harder but settles things over 50mph nicely and that is where your risk lies. 2.5 degrees is okay. When you get to 2 degrees your truck will steer easier but at higher speed it will have a tendency to wander more and below 2 degrees positive it will wander around like a drunk billy goat...especially if you hit a bump or something. This is called bump steer and if you lack enough caster it will take a while to recover as the vehicle at that point is trying to steer itself. And most of the time doing a good job of it. Your sway bar will help but it will not cure an incorrect caster setting in my experience. One other thing worth mentioning...if you have removed leaves from your springs hoping for a smoother ride, it will affect things negatively.

For what it is worth I agree that your wheels (and maybe also tires) are too wide.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end