There is no need to change at this time. You would not see any difference. When you change to 12v you will need to get rid of the ammeter gauge and use a voltmeter gauge. You can get a voltage reducer at napa for ford cars as they kept 6v gauges into the 6o's and that part is still available. Gas gauge may need a reducer by itself and may need a 12v tank sender that is same resistance as gauge.
