The mention of 150 payload was only a method of showing my surprise that payload could technically be that low on a Cummins 2500. Even though the truck is surely more capable the point is that someone doing due diligence on the purchase of a heavy duty truck because of derating of the GVWR it becomes difficult for some people to make an informed decision such as how much over in weight is too much. Met a couple towing a Triple axle toyhauler with a 2500 Duramax. He kept blowing out truck tires. Truck had an overload spring put in but dry pin I was able to find was just short of 4000#. Sometimes its one component that is the weak link. The manufacturers make it a **** shoot determining what will really work. This is not about a particular manufacturer but more for the mildly informed that there is a lot to consider in these situations.
Doug