stock 10 bolt 8.5" 3.73 ratio differential

Need info on installing new ring, pinion, & bearing set. Stock 1/2 ton family suburban, 4wd. Old parts are out new parts are ready. Book says that two washers outboard of ring gear are thrust washers but some people tell me that they are shims (I need to determine if I need different thickness ?). Also is depth of pinion set by torque on the pinion nut or by shims behind the pinion gear? I have paint to look at the pattern but how much gear contact is acceptable. Need Advice.

Harley

[Thanks,
I think I need a new book. There are no 'footprint' pix or description of them in my book. Books always seem to think I'm going to a mechanic unless it's simple.:)

Thanks again Streets. I was planning on the dial indicator and that website & chart are the missing info I needed. I'll have to respond in a few days when the car is back together & let you know how the family wagon made out.
Thanks again.
Harley :)