I have a 1953 Chevrolet pickup truck 235 that is 12 volts. I've had it since 1971 and it was 12 volt when I got it. I assume all the bulbs were changed to 12 volt when it was converted. After about 20 years the fuel gauge quit working because the filient burned in two. So now I just fill it up and note the milage and buy more gas after about 100 or so miles. It has an add on heater as all the older Chevrolet trucks came with heater as optional and had to be installed by the dealer or the owner afte it was purchased. I don't know if it is 6 or 12 volt but it runs good and fast when on high????