duragg, I'm rebuilding my 5spd at the moment and was told about this thread, just read it this morning, Fantastic.
Thanks for taking it to the end and showing all the failures as well, that is where the learning is.
I think someone at Drivetrain.com might be reading this thread, I just measured all of the key slots on my original, WORN 1983ZX syncro rings, .170". The same measurement on the new Drivetrain syncro rings is .155" . Now I don't have to file them!