Is it possible (relatively easy) for me to take the rear end off my 2012 gmc and swap it with my 2005 silverado rear end? Reason being I don't wanna have to change the gears on both trucks when i have the 4.10s and tru trac on the gmc that I need on the 2005 and vice versa.

 

Bump!

 

Leaf perches, shock mounts are different. As for width i'm pretty sure you'll be fine.
Bearings are different on each rear end so you'd honestly be cheapering just buying 2 install kits and doing it.