I'll admit my first stab at it was to buy the Electrical Connections Dyna running light kit to enable rear running and braking lights. Since then I've done two other running light conversions, both using aftermarket dual element signals. Once you identify the rear running light lead it's pretty easy to splice in a line to the signal sockets. The typical aftermarket dual element (ala BellaCorse) has three wires, white for the flasher, black for the running element and black/white for the ground. Yep, the color coding is not intuitive. Standard 1157 stuff tho and not too complicated once you wrap your head around the different wattage of the dual elements: lower for running, higher for turn or braking.
