No power lights etc but ignition turns over?

Hello,

'74 Gold Duster /6 225 basically standard stock set-up. Only an aftermarket stereo that was already disconnected.

Battery is new and has power. The engine started and ran fine all day. Evening (and now) there is no power except the ignition will turn over strong, but not start.

Is there a connection or part early on in the circuit that would cause this?

I'm going over the schematic in the Chilton's manual, but cannot determine what would cause this. Any thoughts?

Thank you.