With those tires going to 4.88's is a little bit of an over-shot, however given the added weight it's still the ratio of choice. You could one day sneak a 34 under there and be really close to stock gearing.
You'll feel the benefit off the line, a little quicker every time you leave a red light.... so your 1/4 mile time might improve from the mid 20's to the low 20's.. On the highway the truck will be a lot happier, particularly going up hills like I-70, you can get away with staying in 3rd a little longer, won't have to drop it to 2nd almost immediately past Georgetown, for example. In general, it will feel like it's easier on the truck on the highway. You still won't be fast though, will just work less hard.
And then in low range, the lower gears will be a huge upgrade- like you can leave it 2nd going down your typical shelf road descent, and it will hold you back at what usually feels like a pretty appropriate pace, without having to use the brakes too much. Having a little more torque in 1st to pop up ledges is nice too, but for me the better benefit was going down... I am guessing you'll get maybe 1-2 gain in mpg fuel economy, so somewhere around an 80 year ROI on the effort, depending on miles driven. Point is you're not going to use less gas, you're going to drive the truck more.
edit: may as well do a front locker while you're in there, if you don't already have one.