What started out a an intermittent no crank has now become permanent on the 65. I can jumper to the starter relay and she'll fire right up. Just no key start.

I disconnected the weatherpack plug (blower/starter) I added in the engine harness back when. Jumpering to the solenoid side of the plug "B" turns the starter. Jumpering across the plug A-B, turn key, still no crank. 

Putting a trouble light on side "A" and turning the key lights the lamp. Placing a meter on "A" I briefly see 12.3 volts then it falls away to 7.5. Hmm. Go upstream a bit and bare the purple wire at "A". Still see a drop there. So it's not that plug.

Inside, since it was a Automatic car, now 4 speed, I have a jumper in the neutral safety switch plug in the dash harness. Measuring the hot side - key on, I get 12.3 with no drop. so I'm assuming the ignition switch must be fine. The shunt pulled and measured for ohms shows no drop in that little jumper. Still no crank after disturbing it all.

Now I pull the bulkhead plug, place a test lead and voltmeter on the firewall side "Start" pin. Turn the key. Nothing, no voltage. Weird.

Storm came, so I abandoned probing the bulkhead plug. Maybe I have the wrong pin? More work needed. I'm going to bring in a hot lead from the battery and contact the neutral safety switch connector downstream side. See if I get a crank. Go from there.

So the the voltage drop is concerning and a tell tale if I knew what it was telling me...

Any thoughts?

I just had a similar issue with no low beam headlights.  Turns out it was a bad connection at the firewall plug.

Had to drive home on the 4 high beam headlights after a cruise night a week ago.

My mechanic diagnosed it for me and got me back on the road again.