I read a posting online the other day by someone with a C2500 GM truck, and he was complaining about only having 2510 lbs. carrying capacity.
With passengers and fuel, that truck would be limited to medium size fifth wheel trailer.
My Grand Design Reflection is 11K dry weight and 2K pin weight--and maxes out my 3/4 ton SuperDuty diesel. I have plenty of towing power, and am not getting any rear end squat with AirRide air bags.
Anyone towing a full size fifth wheel would really do best to get a 1 ton dual rear wheel truck.