Here's a quick and easy way to do this. Leave the rear axle loose in the u-bolts and install the drive shaft. Put an angle finder on the bottom of the starter, front to back. Read the angle. Put the angle finder on the drive shaft just in front of the rear u-joint, front to back. Turn the rear end, up or down easily, until the angle becomes the same on the angle finder as the angle was when the angle finder was on the bottom of the starter. You are ready to tighten the u-bolts.
