Burnt Wire

Clean up all that electric and get stuff - like the fuse box - properly secured. Having stuff swinging around is putting stress on the wires and connections.

1970 is wired basically like this.
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Everything connected to the battery positive is hot.
When the key is moved to Start, the circuit to the Starter relay (yellow) and the Ignition 2 wires are completed. (assuming its in neutral or Drive)
The current will flow directly to the relay which in turn connects the starter solenoid. Power also flow through the coil when the point are closed. The ammeter will show this current. its about 2-3 amps.

When the key in Run, that connects the ignition 1 and the key accessory circuits.