Underdash Harness bunt up

Most 1972 A-bodies have just one power distribution point in the wiring system.
It's a welded wire splice joining the power feeds (alternator and battery) to the various circuits.
It's usually fine. But if there is a problem there, that's trouble. All power flows through it.
The connectors most often are the weak spots. The bulkhead connector has already been mentioned, and on a '72 it would be worth checking the steering column connector as well.

The fusible link didn't melt, so that's indicates whatever the problem(s) are, its not a short to ground.
http://www.heritech.org/cuda/Charge.html