When working with the Ammeter wires......Make sure the battery is disconnected first. Both wires are Hot, and the black wire is NOT a ground. One of the wires comes from the starter relay, and the other comes from the alternator. When you take them off of the ammeter studs and join them, you are simply bypassing the ammeter. If you do this, bolt them together and insulate them really well.
Also, it is possible that the fusible link in the bulkhead connector may have been compromised. So, check that if you are still getting a no power issue.