I can see it was getting pointless.
I just wanted to post what I had posted since I used to build/sell commercial truck in Oakland GMC/Mack/Volvo.
I used to build trucks for folks looking to haul campers (anything actually) but I had a customer that had specific needs as far as his camper shell he was buying. Of course not wanting to order it but also wanting to provide the customer with the right truck for this job the question came up about "What is the bed capacity" without having to calc out the axle ratings, curb weight, camper shell, people, fluids etc...
So after asking around I finally called GM and they told me about the sticker in the glove box. Which was perfect. You see it there but you never really look at it. Or at least I never did, my co-workers I worked with also have been selling trucks for collectively 50 years wasn't aware of the darn sticker. So if anyone can use it, there it is.