I have to disagree with the brakes and steering being the issue. It’s the softer spring rates of the PW creating the issue. My 05’ PW pulled and drove like a 1 ton but sagged like a 90 yr old woman with a very heavy load. Put more than a ton in the box several times, for a very short distance, and ended up snapping both rear leafs at the front eyelets. The PW is the only truck anywhere using that leaf. My 17’ PW drives fine with a load but in no way is it the same as non PW.I don't comment much on here. I have been a tech for 18 years and I have seen alot of over weight issues. In my opinion the truck will hold the weight with the air bags. The truck will drive with the weight. The issue is the design. The brakes and steering are not designed for that much weight in the rear. Not to mention dot/insurance would have a trip with you if something happened. Just a warning seen it before they would void your insurance the minute you are over spec. Also would strongly recommend against anything that long in a 6.4 box. I have a 2500 Cummins I put a sled deck on with two quads. I'm about 400 lbs over weight and I feel thats iffy if I got caught. Just my two cents.