I had somebody suggest just replacing the back of the diff if the internals are undamaged. that plus rebuild the output shaft and I might be back in business.
the gasket for the rear cover on the diff has the same part number for both the M3 and 328 diff.
The rear cover has a different part number for each. So I would speculate that I can use my 328 cover on my M diff as long as everything fits inside.
that leaves me with inspecting and possibly rebuilding the output shaft if needed.
02 BMW X5 // 97 BMW 328iC // 89 325is w/ M50 swap // 06 Audi A3 w/ APR stage II