For comparison, I have a Crew Cab 6.7 with the full Carli Backcountry kit and, on 37x12.50r18s Ridge Grapplers, the truck sits ever so slightly nose down fully unloaded. I've added airbags with daystar cradles and everything works together well. The small lift in the rear compliments the extra spacing for the cradles. I also have a camper shell, spare, and aux tank in the bed (~20psi in the bags). The more you load it up the better it rides. Even unloaded it removed a very noticeable harsh jar/bounce/kidney stab from the rear when the truck was stock. A combination of the add-a-packs, shocks, and tires I'm sure. Overall the truck rides a lot better than stock.
I would also recommend a steering brace if that is not already on your list. Make sure it's compatible with your front lift though. Synergy works with the Carli stuff, not sure about Thuren.
My next steps will be to add traction bars to the mix. The airbag companies do not speak to the traction bar companies though, so mounting both might require a custom bracket. If I did it again I would have added traction bars first. I want to get the wheel hop under control.
I would agree to wait until you have the truck loaded like you expect it will be before you decide on gears. I will be adding 3.73 gears, but I have a G56 truck and I need to get the 6th gear RPM back. The Aisin may handle it differently.
