Need some electrical help with my ‘68 Plymouth Valiant 100

That is good to know! Thanks for mentioning these brands I’m going to reference this for my parts. My uncle is shipping me an alternator he got from a duster or possibly a vailant. He said it should work in my car, but I’m not totally sure on it. I gotta get a regulator too. Would you say rock auto, classic industries and summit are the best place for parts online?
Your car "probably" has the round back alternator with the single field. I would recommend going to the later (1970 I THINK?) square back dual field alternator. I think these guys will agree with that. Just know that with the dual field, the one small wire from the old alternator will attack to one field (doesn't matter which) and theo other field gets grounded. I made this upgrade on my 64 and it charges better and more stable. But be advised, don't go "crazy" with the alternator amperage. I wouldn't recommend going any father than maybe a 50 amp unit. I think mine is like a 37? I cannot remember. It's been awhile ago. But they will probably try to give you a 60 or 70 amp unit. Don't do "THAT".