I killed my 64 Dart GT Convertible.

I would start at the starter relay on the firewall. Does the neutral safety switch have continuity to ground when in park/neutral?

When the key is in the start position, the yellow wire should go hot. If it doesn't then work backwards from there.

Is the ignition switch getting voltage?

Voltage gets to the ignition switch via the welded connection inside the harness. I've read that this connection can be a failure point. If the ammeter has voltage and the ignition switch does not, I would investigate that connection.