Some Chryslers, and a few other makes, seem to have a problem with moisture collecting inside of the distributor cap. One solution is to drill a 1/16 inch hole on the back side of the distributor cap. In fact, some of the early day dist caps came with the hole already drilled in the cap. In later years this hole has seemed to disappear.
Randy designed and built the first 6-volt alternator in 1987. Up to that point there was no such thing as a 6-volt alternator, only modern 12-volt alternators were available.