AAAAHHH.... The light bulb goes off in my head. After poring over all the data in my head for an interminable period of time I finally understand. Find the weakest link in the chain (axle, wheel, frame, springs, tires, etc.), then use that as the maximum payload weight to subtract the actual scale weight of the truck (empty bed with full fuel and cab cargo) which yields the max camper weight. In my case IT IS THE WHEELS (3625 lbs ea.) that have the lowest weight rating and so restrict me to 7050 lbs GVW Rear. I simply need to weigh the truck to find out the real truth.
And then go and buy a camper that is too heavy anyway... : )