Need some electrical help with my ‘68 Plymouth Valiant 100

Snailgarden, don't get too far ahead of yourself.

One problem at a time.

Before you swap out your alternator be sure you completely understand how they work.

This is what you have now




This is the newer style



Be sure you COMPLETELY understand the differences.

There is no reason to change any parts till you KNOW the part is bad.

Pull the existing alternator and find a parts store that can test it.