I'm replacing the bearings in both differentials on my M38A1 (Front: Dana 25/Rear: Dana 44). I've read many discussions and guides on this process and watched several youtube videos and am comfortable with the process but have a few practical questions. Some of the original shims are somewhat corroded and slightly mangled from the process of removing the bearing cups. When I measure the pinion depth shims with a micrometer I get .0117, .0113, .0035, .0035, .0035 (5 shims).
1. Are shims typically standard thicknesses like 3 thou, 7 thou, 10 thou, 15 thou etc. ?
2. How accurate are thicknesses of new shims - is something that measures 11 thou most likely a nominal 10 thou?
3. When replacing shims should I try to select them to get the total thickness exactly the same or should I assume the old shims have been thinned a bit by corrosion and abuse and go a bit bigger?
4. Am I too obsessive about the accuracy of shim thickness - should I replace a shim that is around 10 thou with new one that is also around 10 thou?

I've iterated through the assembly process of my rear diff several times now, I get the pinion preload and backlash within spec and the pattern on the coast side started out looking pretty good with shims close to the originals but the drive side is on the toe and at the crown of the tooth. I've progressively removed shims to move the pinion further from the carrier and adjusted the carrier shims to keep the backlash in spec but my pattern is still not right and my pinion depth shim pack is way less that the original (now closer to 10 thou than the original ~33 thou).

I've read that with worn gears (mine are not new but don't appear to be heavily worn) the drive pattern doesn't give a good indication and I should focus more on the coast pattern. Should I go back to a shim pack closer to what I removed and verify the coast pattern and call it a day?

I don't see any signs that the axel has been assembled incorrectly in the past so I am fairly confident that it was shimmed correctly last time but the bearings were in pretty bad shape.