You can get quite involved with an axle change. Replacing all the rubber mounts can run several hundred dollars alone. Some of those little rubber pieces are very expensive, it can add up. The bearings and seals should all be changed, another expense, this can take some special tools. Just cleaning, sanding and painting the axle is a big job. Getting those rear springs back in requires a spring compressor. If you are switching from drum brakes to disc you will need a different master cylinder and a very expensive rear brake compensator. The compensator is easily over $500.00 from memory. Also all new lines and brake hose. This is a very involved job that can take many hours to do clean and correctly. You also need to align the new axle, you can build the tool, another time consuming job. You will more than likely need all new brakes, calipers and pads depending on the condition of the donor. Have fun pulling the input spline to put in a new input seal, that special wrench is about $80.00 and you are not getting the nut off without it. Even with the tool it is a very difficult job. I used my gear puller pushing on my socket wrench to hold the wrench in place. Also, if you preset the pinion turning torque, as you should be prepared to find a dial reading inch pound torque wrench, another $100.00 or so used on Ebay.If the seal has wore a groove in the input, guess what, you need a new input shaft, or as I did, I found seal that seated in a slightly different spot, so far so good. Don't forget the clean the axle vent also, very easy.
This is a big expensive job done correctly. It is not to bad in an equipped shop, but most backyard mechanics will be making a trip or two to the tool store. Those big nuts on the torque arms are way hard to get off, I think they take like a 36mm wrench and lots of patience and in my case a torch to heat them. This of course all depends on the condition of the axle and car. But most donor axles are going to be as old as these cars and will need all rubber pieces and seals.
