This is something I’m interested in learning, did you ever get around to doing your synchros? I’m trying to figure out how to measure the preload in those shafts.Mine has 90k on it when I did this and my car still shifts great, but I am also wanting to upgrade he synchros as well. I will be making a video of that as well. The toughest part about doing the synchros is, once again, removing the races from the case and shimming for preload. Taking apart the gear clusters is a cake walk. Setting preload on the output shaft can only be done with a special tool that bolts to where the shifter housing is at. It has an arm that extends into the case and rests on either output shaft. Then you dial indicate on the opposite side while prying up on the shafts.
Getting out the races is tough because you run the risk of breaking the fragile oil slingers. For that you need a hook, slide hammer, and a heat gun.
Also, all the shims for the diff can be used for the output shafts preload. They also require no measuring shim, unlike the diff.
This what it looks like to measure output endplay