I actually went and talked to my local tire shop guy this afternoon. I am swapping my current wheels and tires, which are Fuel Contra 18x9 -18 offset on 34x11.5 R18 Nitto RG's, for Moto Metal M0970 20x9 zero offset on Nitto RG's 34x11.75 R20 (295/60 R20). I want a bit wider tread, and not as much sidewall. Plus I have had those same Moto Metal wheels before, and liked the look.
I am also getting the 5000lb airlift rear air bags, and I already have the remote control compressor system for the airbags which I will have installed also. Just so my truck doesn't squat when pulling my trailer. I don't expect a difference in MPG with my wheel/tire swap as the new ones are about the same size and weight as I have on my truck now. I have about 8000 miles on my current tires and wheels and my local tire guy always gives me good deals, so I am doing the swap at a reasonable cost.