thanks to Chris Brown over at C&M hydraulics for giving me the straight dope. The 116 number was only a casting number, but doesn't necessarily describe what's going on internally in the box, so there's NO WAY to tell from that number whether it will work properly on my wagon.

To all who follow:
There's another number on a little metal flat plate on the outside of your box that can be used to determine application.
If the first two numbers/letters are 3V, AK, or A*, the box WILL WORK on your W123.

Mine happens to be A*, so I'm good to go!

__________________
-lee
'83 300CDT (286k)

former proud owner of:
'85 mercedes euro 300TD
'80 mercedes 300TD
'77 mercedes 280e
'80 mercedes euro 250
'82 mercedes euro 250