Help! Dog Tracking!!

Check your bushings on the fronts of the leaf springs to make sure they arn't worn. If everything checks out good with the bushings, get a plumb bob and drop it from one point on each side of the rear end and two points somewhere twards the front of the car, then you can accurately measure how far things are out of whack and shim accordingly. If the back of the car is dog tracking to the passenger side then shim the driver side.