You're making your truck work too hard with 4.10 gears
Go to 4.56's or 4.88's if you plan on 37" tires or for some extra city get up and go.
Electric fans make a huge difference and there are several routes to go. Whatever route you choose, just pick one and do it right the first time over
You will love the electric fans and gears, I would also recommend doing the underdrive pulleys while your fan is out and you have access to the engine bay and custom tunes to tie it all in together
IF you're mileage concerned the fans and pulleys should net you 1-3 mpg average. I saw 2mpg increase on the fans and the gears will help ease the stress on the transmission as well as gain back the hp/tq lost from those 35s