Thanks for everyones input.
Its really not outlandish to say bigger tires would Increase fuel economy, Its simple physics, for example an engine turning a smaller gear (wheel) causes it to spin more quickly than if it were a larger wheel. On the highway with 4.10 gears I figure it would help increasing the size of the wheels greatly, for example instead of the stock wheels, 35-37 inch tall wheels.
Just my thoughts but after changing the tranny and some sensors as of recent, I have noticed some change in mileage for the better.
Additionally I will add I am modding the truck because I Like it and drive it daily, Im also interested in raising its value. Im not actively looking to sell, but almost everything has a price.