wiring problems 74 valiant

If you know very little about wiring you should not attempt to "rewire" the car because you'll only make things worse for yourself. It needs to be diagnosed then fixed properly. You've already spent money needlessly on a new alternator and regulator which could have been easily avoided. With any electrical issue don't jump to conclusions. Buy a good voltmeter and learn how to use it.

That said, your problem as stated above by others is probably at your firewall connector and/or possibly the ammeter. A lot of current flows through the firewall then through the ammeter and then on to the fuse distribution. Any resistance along the way will result in a voltage drop and thus give you problems. Basic Ohms law - V=I/R or E=I/R... look it up. Good luck.