> How was this Mistake Discovered?

Fortunately, it was discovered the easy way. The part number of the
hub is stamped VERY prominently on its face. After seeing the
obviously too-long hub with the too-big hole in the center, I looked
up the part in the ETKA and noticed that the RIGHT one starts with
090, not 087. I poked around and found the 087 part in the Audi
section. Well, OK, I didn't catch the error THAT fast. At first I
didn't notice that it started with 087, and thought that maybe the old
hub and oil seal bushing were some sort of jury rig by a backwoods
rebuilder. It wasn't until after I took a picture of each hub and
looked at the pics on my computer that I noticed the part numbers were
different (three cheers for reading comprehension) and it finally
started to make sense. Swapping the hubs gave me gap measurement of
.091 inch, practically in the middle of the appropriate range.
 The guy at German Transaxle told me it was a good thing I didn't just
try to put it together and try to make it work. I can't remember what
I said, but it was the spoken equivalent of a blank stare. Who would
put together two parts that badly out of spec? If it says shim down to
less than 1mm between, I'm not putting it together till it's less than
1mm! I guess they must deal with a lot of "marginal" installers.