I just saw this so it might be to late to reply but here goes. There was no GM spec on the axle endplay and stock built posi's to date are all over the place. I had in a new loaded,assembled in Mex, posi. Once I removed the huge springs there was over 030 endplay in the clutch stack alone.
Endplay will come from e basic areas or a combination of them.
1- worn axle ends
2- Posi setup
3- enlongated case holes, not too common but I have had to repair them in the past.
Like Tom I tune all my posi's. A correctly tuned posi will not have springs in it regardless of what I see and read online.
If you assembled your diff the common way by checking the lash for 002-008" and you have the numbers you found then you are all set. If it was tuned I would expect it to be closer but a lot depends on the axle. They should be between .185--.200" from face to snap ring and 50-55 rc in hardness.