We have checked about 75 differentials and have found a few that fit, ALMOST and to make that fit we have to machine off 50 to 150 thousands from the center section or add a machined spacer then move the pinon gear to match, there are none that is a bolt in so far and yes we checked the w220's and a lot more.
At J S Benz high performance shop for Mercedes,, i have access to a lot of parts and different years of Mercedes, along with Rudy we are working on it.
with a little modification we could put a sub frame from a Mercedes into our crossfire but then we have to change the hubs,, and calibers , but it would work ,, this could get us a factory posi at almost no cost. if we find the right one that bolts up into the crossfire bolt pattern I don't post much about this because it may not work . just on this subject i have received 6 pm's for info, when i get it to fit either the gear set or the sub frame i will post it. jim