If your talking about power for your stereo and the truck did not have one from the factory..all you need is a pen type circuit tester that detects current in the wires in the dash..you need to find a power supply(wire) that only is on when you turn on the ignition switch to accessory or the on position. Or you can tie into the fuse box and install a fuse in one of the empty places places...or the simplest is probably the wires to the cigarette lighter just make sure you have an in line fuse....radio shack or most autoparts store have them..

 Public library in the reference section has repair manuals such as motor manual or chiltons manuals that would have such information. Either that or contact the dealer and see if they would share the info with you.