Hi First post here. Took a while but managed to pick up a CS with 90% of the body restored.(motor gone). Then got lucky and got a 1991 M5 (rear end hit). I heard from another forum that there was some info here on this swap. Being new to this I have not found any reference ? Any and all help to loacate info would be much apreciated. First question I have is with the rear end. Should I upgrade it to a newer unit ? I thought I read some where that a 1980 ish 525 unit with subframe will partially bolt in then some retrofit required ? I want to start with this so I can figure out which trans to use. with or with out speedo gear. thanks ahead of time for any advice.