With an alternator you will need to switch from positive to negative ground. (Swap leads on ammeter, if you have distributor and not magneto the negative post on coil should go to side of distributor, add a resistor between switch and coil or change to a direct 12 volt coil no resistor required such as NAPA IC14SB.
The points and condenser in distributor don't care if they are positive or negative ground, 6 or 12 volts. 6 volt starter should work on 12 and will turn same way with either positive or negative ground. I would also replace the wiring if it is old and cracked.
Change lights to 12 volt.
I agree with Old, I would get a GM alternator not the kit.