Is it an actual solenoid, not a foot pedal switch? If so, yes, there is a 6V solenoid which would have been used on cars, not trucks after about 1950 or so. If you're working on a truck with a foot pedal start, the switch with the small side terminal resistor bypass will work on either voltage starter. You just don't need to connect a wire to the side terminal on a 6V system. The only 6V trucks with a solenoid start were the Hydra-matic equipped ones.
Jerry
