The short answer to your post is:
-No, not all W116, W126, and R107 use the same flex discs. The 6 cylinder and diesel versions use different ones.
The flex disc itself is available separately, and is also available in a "kit" that includes all new hardware. Therefore, there are two different part numbers. That's not to say that the part number(s) didn't change over the years....because they did.