Can I pull it?????
My 1/2 ton chevy with a 350 v8 claimed to be able to pull 7200 pounds, but wasn't happy pulling a 5500 empty trailer home from the dealer (20 miles on the flat), but it did it. I immediately got the 2500HD (wimpy 1 ton) with 6.0L, which was plenty stable and pulled great on the flat and down hills, but struggled getting the trailer up hills (semi-loaded, about 6500 pounds). It did it, just not at highway speeds.
One of the most likely problem areas with a fifth wheel and a 1/2 ton vehicle is the Rear Axel Rating of the truck. Fifth wheels apply 10 to 20 percent of their entire weight to the rear axel. So even if all the other weights are ok, the Rear Axel weight will likely be your problem area. You can usually tow a heavier travel trailer than fifth wheel, because the pin weight should be less.
For a trailer that size, you will probably need at least a 3/4 ton with towing package. If you don't have hills to worry about, a 'small' (6L) gas engine may be acceptable.
When doing the weight limitation computations, keep in mind that the values you get from the manufacturer are based on the truck being EMPTY. No passengers, no accessories, no cargo, just a 150 pound driver and a bit of fuel...