a puff of smoke and now nothing 69 valiant electrical issue

sketch said
see picture in 31. that gauge the needle went all the way right and disappeared. I reviewed the diagram but i am confused. there is literally no power anywhere. No headlights, no door dome, horn, etc. I used a light meter to check if the battery fried and it is showing power. A restoration mechanic said the whole cluster was shot and the nuts on the back were corroded/worn like someone had busted some of them off and that it was from the electricity coming back when my son hooked the hot wire to one of the bolts that is not the ammeter.

Then he may have but THAT IS NOT THE CAUSE of you not having power. Take a "working car" Let's remove the cluster............Unhook battery.........remove ammeter gauge wires and BOLT THEM TOGETHER AND TAPE THEM. Now, with the cluster completely removed, the car will start and run normally.

So what changed? As I said it's in the diagram I referenced. Follow along for about the third time:

Power comes off the battery and to the BIG STUD on the starter relay which is one of the relay contacts and also a junction point. From there power goes through the FUSE LINK (RED) and to and through the BULKHEAD CONNECTOR. From there it goes inside the passenger compartment and connects to the AMMETER (RED)

So check that far: Power at the starter relay stud? Power at the BIG RED wire cavity in the bulkhead connector? Power at the BIG RED wire at the ammeter? You are losing it in that area somewhere "I bet"