There's a damaged e36 m3 differential at my cousin's shop that was replaced yesterday. I did my diff bushings last week. The mounting positions are different in the rear... they have two horizontal bushings in the rear with bolts that are parallel with the centerline of the vehicle. E46 non-m has a single bushing in the rear that runs perpendicular to the centerline of the vehicle.
As far as the internals are concerned: if anyone has an e46 diff they're willing to donate to the cause... I can prob pick up the e36 m3 diff for free. I'm checking with my cousin to see if they're going to scrap it or not.
Live slow, die whenever.