Jimmy, I don't recall if a '74 had an external voltage regulator or not. I'm thinking it did, tho, so that's the first thing to check. If you don't have a volt meter that will read DC (direct current) voltage, you will need to take your truck in to have this checked out. Best of luck to you.
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them