I was told the 6 volt heaters will work on a 12 volt system. I have 12 volt in my '55 1st series truck. Also have a '54 belair with 12 volt. I am using a 6 volt heater in both without a reducer. The belair has been working for 10 years. They both work well on 12 volt with no reducer. Both are like on steriods. Maybe the electrical gurus might have some input.