I would not be surprised if the RAWR is based on his current tire capacity. When you find which axle your truck is using, you can then get the specifications on that axle to find the limits. For example, my truck runs the Sterling 10.5" axle rated at 9750 lbs. My GAWR was based off the tires that came on my truck even though the same frame, brakes, axle and suspension is used on other trucks with a higher rating than my 6200 lbs. I currently run 4500 lb rated rims with 4850 lb rated tires along with suspension aids to give me a 9000 lb RAWR.