Lance has it right.

a 240D flywheel is fine. Just get it balanced. and make sure you mark your old flywheel. Some are marked from the factory (mine was)
I am doing something similar to you expect i am putting this into a 74 Land Rover.
I got my flywheel off these forums at a very good price (it should be here next week). I had my adapter custom made by another Land Rover enthusiast.
You also may need to make a pilot bushing to go into the crankshaft hole as your tranny output shaft may be smaller than the MB auto. Mine is made from Brass.

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Implanting a OM617.951 into a Old Series Land Rover.