The alignment specifications in the truck manual I've got handy at the moment only go back to 74, which is a little later model than your system. I have a feeling the tread wear problem will not be correctable, due to the major change in the scrub radius caused by the change in the spindle position relative to the angle of the control arms. There is no correction available for the error you have created by lowering. The relationship between the ball joints and the tire centerline has been changed in such a way that the factory-engineered scrub radius has been permanently altered. The best you can hope for is that the vehicle will be safe to drive, and won't have unpredictable and potentially deadly handling characteristics in an unexpected sharp turn or accident-avoidance maneuver. It can probably be made to track pretty straight as long as nothing dramatic happens. Good luck!
Jerry
Thanks again. It will be interesting to see how things unfold. If the geometery has in fact been altered, then maybe a special upper control arm may be necessary to correct it.
By the way, I do have the stock spindles on there. What lowered the truck are 2" drop springs, and 2" lowered control arms. The latter was supposed to be better than drop spindles because they touted that it actually corrected the geometry...it was part of the reason that attracted me to the contorl arms (versus drop spindles).
