Another thing or two...and if you have new leaf springs, etc this should not be the case but if your rear end sits higher than your front end it will by definition reduce your caster angle. I'd get a front end shop to check that angle to see what it is so you'll know.
And also, check to see how your drag link sits. In a perfect world (and the AD trucks sadly didn't all exist in one) the drag link should be parallel to the ground. If it sits lower or higher (not usually the case), the arc of the circle works against you. Years ago I made a diagram showing this. Basically the end of your drag link would make a circle in its up/down travel. Parallel to the ground the arc of that circle is at the "flattest" point for the movement of the drag link end (which will exacerbate bump steer). As you can imagine the further down in the "arc" the end of your drag link end sits, the smaller the amount of movement is needed for it to jerk the control arm further. I hope this helps. Please let us know if you have any questions.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
