Showme,
Maybe an answer to a couple of your questions; turn signals were an option for the 56 that I am aware of, so they were probably an option on your 51 also. My 56 came with just one light on the left hand side at the rear and you provided the arm for signalling a turn. And yes, the tail lights will need a two filament bulb to work as both tail lights (one circuit), and brake/turn signal (the other circuit).
Another Lee.
