As we had problems on the last Safari with the second gear synchro, we have opted to fit steel baulk rings.
The ones we have chosen are Quaife items & have to be lapped in, a bit like you do with valves.
Not the easiest of jobs, but I came up with a way that didn't take too much skin of my hands.
Just wrapping some string around the gear allows it to be turned quite easily. A little cutting paste and get on with it.
After a few minutes, any surface imperfections in the ridges of the grooves on the steel ring have been removed & the ring locks more or less instantly on the gear. Just what you want.
3rd,4th & 2nd were no problem, 1st however has become a little more problematic & it only became apparent when we started to assemble the box. As soon as the intermediate bearing went on fully enough for the circlip groove to show, the gear locked onto the baulk ring. Somewhere along the line, we have lost about 15 thou. Not a lot, but enough to lock everything up.