Some interesting info on the rear diff...
 

I removed the spacers from the stock 3.9 and 4.10 diff here are some neat readings...

Web Ring side Other side
manual 0.242" 0.240"
auto 0.242" 0.238"

Two totally different rear ends/pumpkins and only 0.002" difference! \Maybe I "...shouldn't assemble at home...these are trained professionals..."

Measured with Brown & Sharpe calipers...initially, this would indicate (to me) the manufacturer starts with a baseline spacer on the webring side...think that maybe the difference on the non-webring side may be due to either the difference of the Torsen thickness or the machining of the pumpkin...I will go home and caliper the different Torsens.

I am going to also measure the front spacers too