74 Dart 360 Sport

Definitely water issue with yours , mine was a hack job and because there was a short somewhere to ground it burnt wires badly when they jump wires for 12v to power different areas , lucky it never caught fire on previous owner years back , but probably reason my body was in good shape with minimum rust issues anywhere , I hope to get some more work done with paint this spring to get drive train in
Yeah when I cracked open that white bus and looked at board I pulled it tried nylon brush and some electrical cleaner and it had rust on the board! I knew this was about to get ugly I would basically have to replace most of it. At that point better to upgrade or get all new factory front to back.