With that kind of weight behind it, you really do want the 4.10 if you are going to be pulling all the time. However, I see you are in Nebraska , if you do all of your pulling there, you could probably get away with a taller rear and still be able to pull, but keep in mind that your fuel mileage when loaded will most likely go down unless you can find a sweet spot in a lower gear. You don't mention what tranny you have, but on mine with a 5 speed and 4.10, pulling a 10k 5er even on flat ground, I get better fuel mileage running in 4th and slowing down, it;ll pull 5th just fine with power to spare, but having to keep it floored to do it, just inhales fuel, it does much better dropping a gear and letting it wind up a bit.
Obviously your empty mileage will go up with a taller rear. It's just a matter of what you need to do with it. If you plan on heading out across the Rockies with that load on, you'd probably kick yourself with a taller rear, unless you put some kind of auxilliary box on there ( Brownie, Gear Vendors, US Gear ) to be able to split the gears.