When you think limiting factors, while none of us are the guy that designed the truck, you can reasonably take whatever the max is for another trim level (because you can’t get accurate numbers with class gvw limitations).
IE if the cc dually 4x4 diesel has 5klbs of “rated” payload , but the rc gas 2wd has 7klbs, knowing that “most “ of the weight is going in the bed of either truck, it’s safe to surmise that the 5k lb truck is actually safe closer to 7klbs.
Some will argue this, but they typically are the folks who believe the published numbers but don’t understand vehicles or where the numbers come from.