4 speed ka-booom !

So as all now know the tranny ismostly blown apart. I juat bought a manual. I see on brewers where they talk about counter shaft end play. I haven't been able to get any reference in the manual.
My question is - what are the factory tolerances?
I assume (and I don't like too!) That tolerances are adjusted with different thicknesses of brass shims?
And lastly could I pre check with a dry run ? It doesn't seem the counter shaft would get longer or shorter with needle bearings - lol but I'm asking because I'd be assuming :D