4.10s would make a slight difference on the highway and in town with 31s, but you would see better power also
How big were the stock tires? You'll feel a big difference with 4.10s, but don't think the mpg will change that much
i believe stock tires were 265 75 15, the new are 31 10.50 15, didn't notice any power loss and i know i'll never get amazing gas mileage but any little bit helps
if your stocks were the size you say they were that comes out to 30.6x10.4 so your tire size has not changed much. so if you regear it your going to see power improvement maybe a little less mpg's.
^^thats what the forum is for right, to ask questions about stuff you don't know about i know you re-gear with bigger tires, and the purpose of the 31"s was not to go bigger but because i was in need of new tires i'm just exploring my options to push some more power and mpgs out of my truck, also have looked into a timing bump, e-fans, and underdrive pulleys