I use the factory correct toggle switch on 12 volts and a 12 volt motor, and it works fine. I don't think that it gets any hotter than when I was running 6 volts on a 6 volt motor.
It is a switch with resistance coils in it.
The switch does not know whether it is a 6 volt or 12 volt switch.
Just don't tell it.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission