voltage doesn't matter, a 6V harness has slightly heavier gauge wires, which adds a safety factor - the best thing to do is buy an inexpensive wiring harness for a 50, you can order it with the alternator option .... trying to wire it with off the shelf wire and terminals will not only be a lesson in wasting time, it would be more expensive than a repro harness, not as well done, and leave you with a bunch of left over wire - unless you plan on making all the wires the same color ... and good luck with that
Bill
