any chance you know about the rear plate of the 717.422 and the 717.400.

the 717.422 doesn't have the port for the speedometer on the rear of the gearbox...

I'm putting one of these into my w123 sedan. Just wondering if it's just drill out the blank... or are the castings completely different and i'm out of luck...

I seem to remember that it can be drilled or in some other way adapted to the manual speedo. Someone here knows from personal experience.....The hit man? (screen name)

You may want to compare a parts list between the two boxes. I may be of help. the dealer can too. If you need a 717.400 Transmission part number I will give you mine. I am pretty sure you have to remove the tail section and have the port drilled out. The tail flange and bearing and seal need replacement as well. What you need to know is if the gear for the speedo drive is present. I do have the Shop Manual for the 717.422.
I have a 717.422 as well and am going to need to figure this out too. That is unless i find a 4x4 to put it in. Down the road i guess. Let me know if you want the GL275 Shop Book.

There's alternative path you might want to consider and that is to convert to an electronic speedometer.

You'd need to swap in the speedometer head unit from a suitable donor - an SL, an SD or other appropriate vehicle so equipped. If your manual box has the VR sensor that's it and if not it's a fairly simple matter to make your driveshaft into a trigger wheel and fabricate a bracket for the sensor. This was my solution when I had a mechanical sensor transmission before it failed and I swapped in one that would take the electronic tailcone.

Here's a detailed discussion - http://www.peachparts.com/shopforum/diesel-discussion/312801-mechanical-electronic-speedometer-conversion.html

Here's my driveshaft "trigger wheel" -

http://www.peachparts.com/shopforum/...on-trans27.jpg