What ratio would you recommend for this truck with the way I intend on using it?
What is your tire outside diameter?
Transmission ratio in high gear?
Current rear axle ratio?
Plug it all in here
http://www.onlineconversion.com/bigger_tires.htm last one on the page.
You'll probably want 1,600 rpm at cruising speed, be it 65 mph or 70, or whatever you like. That should be OK for the 6-71 and the intended load, and result in reasonable mileage and reduced "noise" if you call it that

You'll want to turn no more than 2,300 rpm at your fastest speed So if you might need to go 80 mph every now and then for a short bit plan on that too.
Might be you need a single speed rear axle to get fast enough ratio choices.
Would also be nice to have a Roadranger 10 or 13 speed overdrive. If so then I'm guessing 3.54 axle gears with the 0.80 OD in the Roadranger.
How fast do you want to travel, and what are your current measurements and ratios?
Grigg