Agree with jimh425 - we have always bought top line rv's gently used vs the latest new junk offering at the same budget level... people that can afford expensive campers new often look after them while they own them too...
We run an old 06 Dodge 3500 SRW. We haul camper and trailer, or 5th wheel toyhauler or gooseneck stock and flatbeds at around 7000lbs rear axle weight fairly often. It handled the weight fine with the stock suspension (same spring part no. as the same year DRW) and since has that has been modified with a 12000lbs rear air suspension(same as DRW) and 18in tires. It handles weight better with better braking and sway control without any "squatting" but it was ok with the OEM equipment too.