What kind of terrain do you plan on doing? Super low ranges are great for rocks and severe obstacles but may be too low for just trolling around the desert. Sometimes I find my low range too low, and high too high. It's like I need a gear or maybe 2 between 3rd in low range and 1st in high. So, freeways are out, good that decreases the choices. How big of tire do you run? Do you need or want to be able to spin it? Muddy and loose where you are? Best for one size could be worst for another. In most cases for just general blasting around the stock gears are fine, but if you really want a lower overall gear range, depending on the transmission type man or auto, you could go to a 4 to one low or combined to lower your OVERALL ratios. Have you changed anything else in the truck?
As for towing, what type of trans is it? Auto or Manual?