Took delivery of my 2021 FX4 Platinum with 3.31 a couple months ago. Went with 3.31 because I rarely tow anything, BUT, since I've taken delivery we've been looking at travel trailers with GVWR 6000-6500 lbs. I have a 2" level and tires are slightly bigger than stock 275/60R20 up to 285/60R20. Will I have any issues towing in the mountains? Does locking out gears, which I've never done, help? Should I change my gears to 3.55 or 3.73? Truck has a tow rating of 10400 lbs. but I know there are lots of other factors to consider. Looking for thoughts and advice as I love the truck.