My truck 52 1/2 ton has the "old" 4 wire turn signal switch. That means I have a set of lights just for turn signals. Original lights for Brake and Tail lights. Looks good to me with both sets of lights on the back. Newer switch will integrate the brake lights and the turn signals. More wires than I have. Brake lights are tied together through the switch for the brake switch and separated for tun signal function in the switch. Original turn signals were a Dealer option and set on top of the front fender. Mine were just a ball of rust and not repairable. So I moved them to the park lights in the grill. I hope this helps and not confusing you. Look at the wire diagram and trace with colored pencils might help.
