Is your turn signal switch built into the steering column, or is it an add-on that clamps to the column? "Signal-Stat" made two add on units, one with 5 wires and another with 7. The 5-wire unit was designed to be used with separate light assemblies front and rear for turn signals. The 7-wire ones have a discriminator circuit that allow the same rear bulbs to be used as brake lights and turn signals. Later model trucks that came factory-equipped with turn signals also used 2-filament bulbs front and rear to combine park, brake, and turn lights in one bulb housing, both front and rear.
Jerry
