There are specialty shops that perform this work. It can be done. The next issue is it worth the considerable cost, or more practical to purchase a larger truck? Phone around to large truck repair facilities and inquire, when you locate a shop it must be certified by U.S. DOT to change the weight ratings.
This may involve replacing the entire suspension system, drastically altering the drive-train, braking system, wheels and tires, etc., because the rating is limited by the weakest link.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"