checking rear end housing straightness

If the axle is out of the vehicle, put it on a pair of jack stands on a level garage floor. Mark the tubes at three evenly spaced intervals and measure at from the bottom of the tubes to the floor. Use another jack stand to hold the center section at the pinion and rotate the center section 90 degrees and repeat. If you need a slightly heavier duty replacement with much better parts availability, find a 7.5 inch axle out of a ford ranger.