Stay away from the little tin-box add-on regulator, it's cheap and will blow up. Get the correct isolated stator alternator, (2 wire), for the vehicle and wire it per the stock wiring diagram with correct regulator. The extreme high end of the voltage range for car operation at 70Amps is 15.6V. We used to test 10A mobile radios at 16.2V but just to make sure they wouldn't blow up. Nominal charge voltage for a 6 cell lead-acid car battery is 14.4V, a normal system shouldn't get much above 15V.