No Power to anything

71 Duster with a 340. The problem-no power to anything, no dome light, no headlights, no wipers, no ignition power. The car had not run for 12 years. I just rebuild the engine and put it back in. Went to start it up and had no power to anything. One day I go out and there was power to everything. It was a miracle and had not done anything to it. It was like that for a couple of days and now it is back to having no power to anything again. I know the battery is good and the connection to the battery is good. I have a good ground from the engine to the firewall. I do have power to the starter relay. I studied the wiring diagram and read several threads on here. I wanted to run my conclusion by you experts. With my test light I followed the red wire that go's to the ammeter. I have power at that red wire side of the ammeter but no power at the black wire side of the ammeter. Could this be my problem? Can I bypass the ammeter by connecting the red wire to the black wire terminal?