[mully]

I have a 2002 4x4 chev silverado 1/2 ton pickup that I need for towing. I have done a few mods to it like upper grill block, partial bellypan, lowered ride height 2" front and rear that has helped.
Next I was going to try different size tires. It has the stock size tires on it now (245/75-16 on 16"x6.5" rims) max sidewall air pressure of 44 psi. Was thinking of trying a 215/85-16 E rated tire with a max sidewall pressure of 80 psi. Even though they are thinner tires (1") they are higher load rated tires (E-rated) and the diameter are roughly the same.
Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/75-16 7.2in 15.2in 30.5in 95.7in 662 0.0%
215/85-16 7.2in 15.2in 30.4in 95.5in 664 -0.3%

My question is will this help my mileage much or will I just get a rougher ride and less traction? Guess I'm just asking for pro's and con's on this type tire change.
thanks