Mine came with the towing package which included the 7 pin setup. It is best to install the 7 pin setup. There are adapters you can get to use any of the 4 pin setups. The wires and adapters are available at any parts stores, even walmart. Easy to install with the trailer wire adapter kits it will give you all the wires you need without messing with your existing harness.

 

Bump187, the 7 pin allows for 12v to power the fridge while in transport, plus trailer brakes, if I remember right, the 3rd one is for charging the small battery for the break away switch, plus the other 4 pins for lights. If your trailer only needs/ you want trailer lights, a 7pin to 4 pin converter will work. If you want to power the fridge and break away/ use trailer brakes you will have to wire in a 7 pin or get a plug-n-play wiring kit for the truck.Your standard 4 pin does not allow for constant 12v power at the connector. So depending on your trailer and options.
If your towing with an automatic tranny, I would go with the biggest tranny cooler you can install. Heat kills an auto as I am sure everyone knows, a t-cooler is just cheap insurance.