There are actually two thickness Thrust Washers available, one is 0.035" Thick and the other is 0.048" (from memory). Just grind a tad off the 'pip' on the output shaft, doesn't need to be precision as when the car is in motion, the gear thrust out (towards the Thrust Washer) anyway, hence why there is only a thrust washer on the outside and not the inside.
I don't actually use those crap fibre thrusts (in a stock diff build), they don't last and break up pretty easy. Not sure if you guys got them in the UK, but all out early gearboxes had Brass Thrusts, certainly all the 3 Synchro Boxes and a few of the early 4 Synchro had them. I'm just about out of them now, and will be making some once they are all gone. Fit and forget.
Edited by Moke Spider, 16 December 2014 - 08:00 PM.