Dana 60 info and help

Need some help with a Dana 60 gear swap.

I have a Dana 60 from a 69 Charger in my Dart and I'm in the process of switching out the 3.54 gears to 4.10's.
The 4.10 gears are used Richmond gears.
I've set the pinion depth but when I mocked up the carrier I have at least 1/8" backspace and I can see that there are only maybe .030" shims under the passenger side bearing so even if I remove all those shims I will still be no where near the correct backspace. :banghead:
From what I've read I should be able to use up to 4.10 gears without using a ring gear spacer.
What am I missing?

Thanks