I made a heavy duty work stand to straighten rear ends and shorten them. To straighten them I use a 1.5" tri bar run thru the housing with bushings where the bearings are. Working on one end I slide the bushing out and use a hyd jack to move the housing where the bushing will side in. This takes some time to get just rite. When I shorten a rear end I make sure the ends are square as I'm welding them. After all the welding is done I straighten the housing. I have rebuilt and straightened several rear ends and only one housing did not need straightening.