Ok so I found this document about various 124 Diffs, it seems that for the 4matics, the 300E and 300TE diffs have different ratios. Maybe this file will be of some use to others.

http://www.w124performance.com/docs/mb/other/differentials.pdf

I still cant find out if the front coils are common to both cars...I have to assume they should be, but I wonder if anyone can confirm???