Gudday Tim,
I think all the info you are chasing might have already been covered in the Hi-Po Shop forum under the heading
"G.M. 10 Bolt rear end question".
A posting from Lindsay (GMCanuck 4/17/08) inludes a link to a GM rear end ratio calculator.......mmmm very handy!
Have a read anyrate......some interesting stuff !
All the best....Doc Bob