If I'm following this correctly:
- your diff axle seals were leaking, so you ordered new axles? Why not just the seals?
- I know the welded axle/bearing issue. On mine, the diff carrier was weldedto the stub axle... Took some serious beating to get it out. Fortunately, mine was salvagable with a little work.
(edit: I just noticed you don't have seperate stub shaft and axles like the SLK32... Odd)
- the 300 may have the same tranny, but the rear is different (think it shares the older E55 Benz). I'd imagine the TCU is flashed for that gearing. Also, i believe it is 2" wider, & longer so your stock axles/drive shaft won't work.
- what was the code you got with the 3.27? I still may try mine to try and get it to work...

I'm thinking it's time to call Quaiffe and tell them we have enough interest for a real LSD...