I am a full-time rver. Been through/to 27 states and so forth. We started with a TT 32' and then upgraded to a 5th wheel at 42' in length and kept same truck.
Here are keys weights you need to know of and to stay in:
Trucks GCWR = truck and trailer TOTAL combined weight
Trucks Curb/Dry weight
Trucks Wet/Load weight
Trucks Payload
Trailer/5th Wheel Curb/dry weight
Trailer/5th Wheel Wet/Load weight
My truck is a 15 RAM 2500HD 4DR. 6.4' Bed 4x4 6.7L Cummins, my specs are:
GCWR: 25,300lbs
Curb/Dry weight: 7,310lbs
Trucks Wet/Load weight: 10,000lbs
Trucks Payload: 2,690lbs
Max trailer weight: 17,510lbs
My 5th wheel is a 17 Forest River Wildcat 38MBX 41.5' in length w/4 slideouts
Curb/Dry weight: 11,187lbs
Trailers Wet/Load weight: 13,609lbs
Hitch weight: 1,100-1,200lbs
So for GCWR, if both were maxed out to their limits both together combined weight would be 23,609lbs. A 1,691lbs under the TOTAL combined weight allowed to be safe and legal.
From the trucks curb/dry weight you have to account for everything in the truck like: fuel, coolant, oil, passenger(s), luggage, coolers, hitch, anything that is not part of the curb/dry weight. So all that I just mentioned plus curb/dry weight equals new trucks weight then add hitch/pin weight and hope your under the trucks max Wet/Load weight.
For hitch itself I use Anderson Hitch, super strong, lightweight and super easy to hook up to compared to standard 5th wheel hitches.