You can see the bump stops mounted to the frame and they show your rear end is not mounted right. The original rear end had spring pads that were not centered on the rear end, they also had a bushing in them that allows the rear end to pivot as the rear end moves up and down. This is needed because of the torque tube. Your best bet is to measure the wheelbase as truckernix suggested. This will get your rear end in the correct place.
