Perhaps you had "Vas ist Los?" in mind. [Literally, "What is loose/wrong/amiss?"; figuratively, "What's up?"]

The simplest solution for this situation is:
1) For the diff, use any 81-85 380/500SL or SE center section that has a LSD. All are 2.47:1. OR, use the internals from the 560SL/SE diffs, in your case. Also 2.47.
2) For the trailing arms, install all the 560SL components in your subframe.