What you need to do is obtain the parts list for both the 717.400 and the 717.422. Then you can figure out what needs to go into the replacement. I will look them over soon and see if I can help.
The dealer is usually happy to supply printouts and diagrams with part numbers. That will help. I have them for the .400 but not for the .422.
Remember the output flange can be replaced. Not sure if anything else needs switching over. Thats where the parts list comes in handy. I believe there is a cog on the output shaft that makes the speedo drive turn. You will have to check. Did I mention I have the MB book on disc for these I can share if needed.

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Chris
84 280sl
82 300d euro