what can i pull?
Ben, GVWR is the MAXIMUM weight your truck is supposed to be at, with all fluids, passengers, accessories and cargo. Exceeding this may or may not cause your truck to wear excessively and/or cause an accident. But exceeding any truck rating greatly increases your chances of being taken to the cleaners by lawyers after an accident.
There are also maximum weights for the front axles (generally not a problem) and rear axles (with a 5th wheel, this can easily be exceeded since 10 - 20% of the trailer weight is over the rear truck axle). Generally in a 1/2 ton pickup there is only 500 - 1000 pounds difference between the truck empty (curb weight) and the GVWR, and don't forget that the 4x4 option is not light, and neither is a (good) hitch.
As DL says, the GCVW is the MAXIMUM weight of both the truck and anything hitched to the truck. So if that is 12000 pounds, and your truck is 5500 pounds by itself, that would allow for a trailer of 6500 pounds. So I don't know how they can claim a maximum trailer weight of 7200 unless your truck is really light for a 1/2 ton.
Historically, towing more than 5000 pounds with a 1/2 ton pickup truck has been unsatisfactory. The newer trucks seem to be getting more efficiant at towing, so perhaps that is no longer the case. Also, a higher gear ratio seems to make for better towing, at the cost of low end acceration and gas mileage.
So, your first step should be to find a vehicle scale, and weigh your truck fully loaded with everything and everyone you plan to carry (including a full gas tank). Also get the weight on the rear axel so loaded. Record these critical 'curb weights'. This will tell you how much weight you can add to the truck via hitch and tongue/pin weight. You may find out you can pull a heavier travel trailer than you can a 5th wheel, since travel trailers apply less of their weight to the tow vehicle than 5ers do, and the height is less for less wind resistance.
One last thing, remember that gas engines are not the best for pulling a load up a hill, and 318 is fairly small as gas engines go. If you do plan to tow even 5000 pounds up a hill, be prepared to do it slowly
And if you don't have a transmission temperature gauge, get one, cause most transmission problems are caused by fluid breakdown, and overheated fluid breaks down very very quickly.
If you do go with a travel trailer, pay close attention to the hitch you get, and get the best you can. Travel trailers can be the 'tail that wags the dog' if the hitch does not have the correct features or is not set up right.
Oh, and another thing. When you do go looking for a trailer, don't pay much attention to the 'dry' weight claimed. It is not reliable (may not include all the options installed in the trailer) and does not include luxuries you put in the trailer, like food, water, clothes, and the parts to allow you to hook up to electricity, water and sewer. Its a good idea to take a finalist trailer to the scale and see what it REALLY weighs empty. If you shop for trailers by their GVWR (maximum weight) you are less likely to exceed your truck ratings, and if you get the true dry weight, you know how much stuff you can cram into it.