You would be better off posting this in the technical section. For starters, I would find the chassis diagram and measure it up well to make sure everything is build on a solid base. For the issue you mentioned on the rear axle and the different gaps between the wheels and body work, one of the things that could cause this would be a leaf spring that is going soft. A sagging spring would allow the spring to flatten out more, which also would move that wheel a little farther rearward than the wheel on the other side without a sagging spring. You can see this in several ways; 1. the sagging spring would have less arch in it than the good spring and 2. the shackle on the sagging spring would be angled farther back than the other shackle.

For your fan issue, I would check the motor mounts first and make sure the are all in good order.