My 41 original only had two wires to the rear lights. One for when the headlights were on and one for the brake lights. When I changed to blinkers I used dual filament bulbs. For this reason there are three wires going to my tail lights. One to the right, one to the left and one that is for when the headlights are on. I had to also modify the sockets for this . Due to the age of the wiring all of the wires were replaced.