It's a feeling like working on women.

I grab the crown with my hand and feel for any play sideways. If any I add 0.10 shims on the right side and continue. When play is gone I add one more to feel if the crown wheel can turn freely with no biting at all. Also look at the needles, they must turn when turning the crown. If you replace both crown wheel bearings, I have a fraction more load again free spining crown wheel since the load changes after the bearings are seated.
Citroens way is to measure the depth of the output hub and the distance from the face to the bearings outer race but each side of the gear box and the hub are not the same. I mean you don't get the same result on the same hub, measurering two different places. They are never 100% flat or even.
You can do all this without the paper gasket, when completely finished just add one more shim of 0.10 (same thickness of the paper gasket)

Hello, so now I am finist assemble and adjust the gearbox.
Do not know exactly where the parts come from, but now I have the following gear.

4. gear 5,1/1
3. gear 6,85/1
2. gear 10,2/1
1. gear 20/1
(this is the total gearing, from engine to driveshaft)
It will be exciting for the summer to get out and run with it