Light 5th wheel
What is the engine in that pup? I had a lite Terry 5ver which only weighed about 6000 pounds (24.5 feet), and my 2500HD with 6.0 gas engine struggled to get up hills. Also, 5vers put a lot of their weight (10 to 20%) on the rear axel of the truck, which often exceeds the axel weight rating of smaller trucks.
If the truck has a tow package, then it should have a tow rating. Keep in mind that this rating is usually with no cargo or passangers in the truck, just a 150 pound driver and a bit of gas. Look for a trailer with a GVWR of equal to or less than the tow capacity of the truck, minus anything else you will carry in the truck.
You may find that a 5ver is just not practical. You may have to go with a tiny towable or some form of pop-up. If your reason for looking for a 5ver is the easier towing and hookup, check out the PullRite hitch which claims to make towing a trailer just like towing a 5ver.
Or you could just get a real truck