converting wr headlight to 12 volt

Anybody have any experice or idea's with converting a 79ish wr headlight to a 12 volt bulb ( i'm only guessing it was 6v from factory because of the extra 6v bulbs that were given to me when i bought bike) --- I went to a mzb ignition and it has 12v 85watt light capacity--so i'm looking/hoping to get somewhere around 80 watt bulb although a 50/55 watt bulb would be a start. i'm guessing i'm going to have to make a newer type bulb fit in the bulb socket of light deflector.