Re: Newbie has Questions:
The first thing you need to get corrected, and it may be the only problem, is the toe-in. As the name implies, the front wheels should be closer together in the front than in the back. If you are a half inch wider in the front, then you are toed-out, which will cause the truck to wander as you have described. I assume that you measured somewhere on the tires, because a half inch of toe-out at the wheels would be almost un-driveable. Toe-in should be measured at the wheel rim. The toe-in spec for straight axle GM 4X4s is normally between 3/16" and 3/8", except for full-time (NP203) trucks, which should be set to 0". This is easy to correct, and should be cheap to have done at any alignment shop.
'70 CST Blazer, 350, SM465, NP205.
'87 Suburban 4X4, 350, 700R4
'88 Chevy PU, 4X4, 350, 700R4