Resurrecting this thread. My father and I recently acquired another DC93 E28 M5, 2875122 and recently put it up on the lift to examine and create the tome that will be the parts list.
I noticed the poor condition of the differential mount and it ran through my head there was something very unusual about that part. I couldnt place it, so I checked on RealOEM, the price $256USD. Sounds a bit high for what it is, but not out of order for 31 year old M car. Then I put into the search engine and clicked on Turner Motorsport . . . $450 LMAOOOOOOO. Clicked on Bav Auto, $480! That was the issue, this part is priced far above the seemingly equivalent non-M E28/E24 parts. I even checked rockauto to see if they had anything from their array of suppliers, nothing.
Im not going to spend $450 on this, Im not EAG with the OCD mindset.
So options, get the M535i part as mentioned by davidoli. Easy.
Get the E34 M5 part, which is pn 33311132251 and see if this is another possibility. $136 and also fits the E32 750i so perhaps this is an upgraded part that can handle the load paths better.
I put my name down for the "bombproof" diff mount on bimmerforums. Interesting design, surely will increase wear to some degree but I think it might be worth investigating. Hopefully enough people are interested to get another run. Probably $250-300.
So Ill spend more than the $450 in the end, but thats sort of how this goes.