I am looking at 2 trucks, a 2020 big horn loaded and a 2020 Laramie loaded. My questions I have are, gas milage on them with the 4:10 gears or the 3:73 gears, I do medium towing but we will be getting a 5th wheel toyhauler down the road. Feelings on the 6.4 gasser? There is only a few hundred...