The front and rear housings were matched, and serial numbered together on the assembly line. The tools used above were required to align replacement parts in case the matched assemblies got separated or one was damaged in some way. Yes, it's a royal pain to get mismatched parts to work well together. Rapid wear and vibration was usually the result of trying to force-match front and rear sections without going through the alignment procedure. I grew up around a shop where they did things the right way the first time. Until I started working in other shops, I didn't realize how much half-donkey work was done on a routine basis! 60+ years in the business hasn't changed my opinion of a lot of so-called "mechanics"!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!