I have done the Timbren, Superspring, bigger tires, etc. etc. and never gained as much as when going from a F-150 to a F-250 or from a 1500 to a 2500. I might have gained a little stability, but really did not change the capabilities of the pickup very much. If I want a vehicle that is good for 9,000 pounds total weight, I purchase one with a gvwr of 9,000 or more. One can play with axle and tire rating to come up with something they "think" is better, but I let the engineers at Ford and GM do it for me. They "might" know a little more about the vehicles they build than I do. I still think advising anyone to exceed their gvwr is not doing them any favor, and that is what the OP asked about.