Towing capacity for the truck is empty and figuring one person 150 pounds as the driver. So if you add people to the truck you reduce tow capacity. Tongue weight is also critical. you may want to get a car hauler instead of an enclosed trailer. You definitely want to look for trailers with brakes.
Tow capacity is minus all the weight you add to the truck. So the more in the truck the less you can tow.
Here is a guide to help you...
Although "payload capacity" usually refers to how much weight a truck can carry in both passengers and cargo in the cab and bed, towing capacity refers to how much the truck can safely tow. Although different, these two parameters can affect each other. For instance, the payload can include the tongue weight, which is the portion of trailer weight -- usually about 15 percent -- that bears down on the truck's hitch.
Manufacturers often embellish the maximum towing capacity of a truck in advertisements. For instance, they often calculate this number by supposing that nothing is in the truck except for a 150-pound (68-kg) driver. In realistic situations, where the driver may be heavier, other passengers are in the cab and extra cargo is in the bed, the truck's actual towing capacity is lower. In general, the more pounds in your truck's payload, the lighter your towed vehicle should be.
Here is a guide to help to determine towing capacity. And a brief explanation of what all thise dam abbreviations mean...
Finding Your Vehicle's Compliance Certification Label
After you've read your vehicle owner's manual, it's a good idea to double check the compliance certification label. This is typically a sticker placed somewhere in the driver's door sill area. This label will have several fields, labeled with acronyms such as "GVR," "GAW," and "GCWR." These fields are defined as follows:
Gross Vehicle Weight (GVW)
This is the vehicle's standard curb weight, plus an allowance for a standard amount of luggage, gas and passengers, as predicted by the manufacturer. Of course, your vehicle's actual weight will vary depending on how much luggage, gasoline, and passenger weight you have actually placed in the vehicle, so the GVW is an approximation.
Gross Vehicle Weight Rating (GVWR)
This is the maximum safe actual weight of your vehicle. If you exceed this weight, the vehicle's engine, transmission, brakes, and so on will be stressed beyond their design limits.
Gross Combination Weight (GCW)
This is the actual weight of your vehicle (GVW) plus the actual total weight (not the tongue weight) of your trailer. This number must not be higher than your vehicle's GCWR.
Gross Combination Weight Rating (GCWR)
This is the maximum safe weight of your combined vehicle and trailer. This weight includes all people, luggage, and other material. If your combined towing setup exceeds this weight, your vehicle's engine, transmission, brakes, and so on will be stressed beyond their design limits.
Gross Axle Weight (GAW)
These numbers are the weights expected to be placed on your vehicle's front and rear wheels. The two numbers are likely to be different to account for engine weight and other factors.
Gross Axle Weight Rating (GAWR)
This is the maximum safe weight that can be placed on your front or rear wheels. The two numbers are likely to be different to account for engine weight and trailer tongue weight and luggage. If you exceed this weight rating on either the front or rear tires, you can create a dangerous driving situation or even damage your vehicle.
Every modification you do to your truck effects weight carrying capacity and towing capacity...
hope this helps a little...
