Thats too bad the bellhousing pattern is different totally. It might have been very easy otherwise. Since mercedes was such a low volume producer there is still a chance the internal part numbers might be the same.

That is the safest way to approach this in my opinion. Especially if the basic gear ratios remained the same for both transmissions then it is easy. If not it becomes complicated somewhat again.

This said there is still a small chance of simularity. Cost of re tooling is substantial if not required. They just might have gone the cheaper route.