Fusible Link ... that makes some sense. Got some power (briefly) when I wiggled the ground cable. Might have also been moving the fusible link wires on the positive cable.

So ... if that is the problem ... would anyone like to guess if I can get ignition by jumping the starter?

 

Just went out and wiggled all the cables. I can get the lights to come on when I fiddle with the ground cable. That might not be my only issue, but its where I'll start.

 

When I was still in high school or just out, around 40 years ago, I had a similar problem with my '65 Mustang. Turned out to be a bad connection at the starter. I removed the cable and cleaned the terminal on the cable and the terminal on the battery and that solved the problem.

The symptoms you report point to a bad connection somewhere in the primary starter circuit, I think, or perhaps at the battery. It could also be the negative battery cable. Remove and clean it at both ends - at the battery and also at the other end where it connects to the frame (or the engine; I don't recall)

The faulty connection, wherever it is, is good enough to power the lights and accessories but is not good enough to handle the high amp load demanded by the starter.

 

Replaced the negative battery terminal ($6.99). Took apart, cleaned and applied dielectric grease to all ground connections ($1.49 for the grease). Tightened. Started right up. Fascinating that there were absolutely no early-warning signs. Glad that's over!

 

Thanks to all for your help.