My 2005 Ford F250 carried 2750 lbs empty on the rear axle, 7000 lbs with my 4000 lb truck camper and 8000 lbs once I hitched up my 8000 lb enclosed trailer on 28" extension with WDH. The truck had the camper package (heavier front coils, upper rear overload, rear stabilizer bar), but I added 19.5" rims and tires, Rancho RS9000XL shocks, Firestone Ride Rite air bags, upper and lower Torklift StableLoads, Torklift tiedowns and FastGuns, 20K lb SuperHitch and 28" SuperTruss
I drive roughly 10k miles a year with the camper and 75 percent of the time with the trailer also in tow. At least one trip a year typically takes us over the Rockies and most cross the Sierra's or Cascade's.