I do have one problem with the thrust race issue. You will notice that the spacer is now on the other side of the thrust race as compared to the bearing. This will mean that the spacer now when the diff is acting will turn in the opposite direction to the part of the shaft which it is wrapped around. Potentially there is the opportunity for some friction there. I picked up a Boca Thrust race afew weeks ago, I will be machining my own spacer so there will be no chance of contact between it and the shaft, also I will make it able to locate on the inside part of the thrust washer so that will not rub on the threads. I'm waiting for my aluminum bar to arrive so I can make this. I like the idea of using a propper thrust race rather than the bearing but I think those issues need to be addressed before a "perfect" solution is available. The only problem I think I will run into is having exactly the right length for the spacer I need to make. To make the spacer work I will only be running one bearing in the hub and it will be on the inside near the diff plate.
Chris.