I suggest that you study this wiring diagram. Based on what I can best determine turn signals were a dealer installed accessory for trucks in 1954. This included adding a second dual filament taillight to the right rear of the bed.
Your latest picture only shows 3 wires in the harness from the steering column. There should be another 3 wire harness going up to the turn signal switch. It has white, pink, and purple wires. 1954 Truck Turn Signals
I am completely confused by the double dual filament tail lights. Until you can trace all the wires to all the filaments I doubt if I can offer much more guidance.