It's not a matter of wheelbase or bed length. With a 3/4 ton truck and fifth wheels, you're going to be limited by the rear axle and tire capacities. Most fifth wheels now have 23 - 25% of their loaded (think GVWR - not dry weight) weight on the pin. 23% of 14,000 lbs is 3,220 lbs. Once the truck is loaded with occupants, fuel, and a hitch, you're not going to be able to put that kind of pin weight on it. Ask me how I know... Any of the three American-made diesel light trucks will pull a house off it's foundation - you just can't put the weight of a house on the rear axle.
Rob
