On a 56-?? truck (or, an earlier truck converted to 12v), if you leave a 12v 2-or-3 position switch on, both will provide a live and full 12v feed to the coil.
A 2-position switch was standard equipment on at least 47-55st Advance Design trucks (all were 6v). For this thread, let's ignore 6v solenoid starters on 54/55 Hydra-Matic trucks.
The later 3-position switch was designed to provide a full 12v feed to the coil when cranking; and, when not cranking, the switch is intended to run a 12v feed through a ballast resistor into the coil.
