If you PM AcademyUK then he may be able to provide you with a part number for the new diff screw/thrust race set for the SB. We had an issue of shearing diff screws, and it came from the fact that if the diff is left to slip, a small groove would be worn into the diff screw, so when you go to tighten it up, it would shear.
The new screw is much thicker.