Quick note on gears:
Lots of people say go with 4.56 gears, but I'd actually go with 4.10's on the new trucks. The old trucks, back in the 4 speed days, had much higher gears for first and second than in the new 6 speeds. I think the first gear on the old 4 speeds in your pre-2007 trucks was like 2.48:1. In the new 6 speed transmissions its 4.027:1. In other words while the old trucks needed 4.56:1 gears to get their power back, going with 4.56 gears in the axle in the new trucks is going to be overkill. The second gear on the new trucks is 2.364:1, so its almost as tall as the old transmissions first speed.
I'd go with 4.10's for now. Otherwise, your highway mileage is going to really, really stink. Dodge did something similar with its new 6 speed transmission, and when a buddy of mine lifted his 2010 Ram 1500 and put in 4.56 gears he liked how zippy it was around town but he was cruising on the highway near 2400 rpms, unloaded and on a flat surface at 70mph. You could be looking at the same deal in a thirstier 6.0L in a heavier truck, and gas is $4 a gallon.