To really determine the answer you need to know two things. How many amps does the 12 volt motor draw at full load verses the number of amps the 6 volt motor drew at full load. The second thing would be more of a personal choice. Is the fan speed at the low and medium switch settings on the original switch acceptable to you?
My 12 volt replacement motor draws 3.8 amps at full load. Does anyone know how many amps the original 6 volt motors drew? I can safely use the original 6 volt switch if the motor drew 8 or more amps.
