Everything on the trucks run on 14 volts. That is the voltage they are designed for. The reason 8 volts will burn out bulbs & acessories is that 6 volt trucks run on 7-7.5 volts & 8 volt battery would have to be set on aprox. 9 volts to charge. If you have 14 volts at the alt. you will have 14 volts at the tail lights.
