M&M,
Could you be a little more specific as to where you are mounting them, how many, what style light you are thinking about. I am not too sure about why you would use a 4-conductor wire?
Maybe this short summery would help?
Most like to have there marker lights come on when the trucks parking lights are on, so you would tap into one of the trucks parking light circuits, the rear tail light assembly is the easiest place to access the wires.
LED's are very polarity sensitive, they must be hooked up right or the will not work, also they can cause other lights in the circuit to not work as well. Some lights come with the polarity (+ or -) printed on the back. Others do not, so you would need to figure it's polarity out before the install. Number one rule when replacing the vehicles existing lights with LED's is to do one lamp at a time, make sure it and all the other lights are working, then go to the next.
When installing a group of lights, like on the air dam or along the bottom/side of the truck, it is best to run one wire for the + positive wire and one for the - negative wire. It may be easier to run only one, the + wire, and ground the negative wire with a mounting screw, but they corrode and generally are a pain in the butt. A little more effort now saves you latter.
If you are going to go ape **** and have many lights, then use a relay and make your own circuit, make sure it is fussed and well guarded.
Good Luck