Those things have been unobtanium for a long long time. I've reused them with great success. Mike's procedure above is spot on. Other than that, rebuilding is just like any other rear end. You won't get the bearings off the axles without a bearing puller, and you need an inch pound torque wrench. Others have made aluminum spacers, but that requires paying a machinist to make it. In most cases the side shims can be reused without changing them to different sizes, it's just the pinion bearing making all the noise. You can also research Rover SD1 rear ends. They are one and the same. Available gear sets were 3.08, 3.45, and 3.90. There were also 2.84s in some SD1s, but those are hens teeth.