Dumb question

OTH, the wires through the sheet metal needs to be addressed as soon as possible.
Without the grommet, or something like it, it won't take much to cut through the wire insulation.
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And the snipped wire (in circle) isn't much better.
Tape it. Find out what its for (get a '66 shop manual).
When you take the connector off, that terminal can be removed if you're not using, or replaced if putting back into service.

One more tip. Power is distributed in several places, not just the fusebox. The starter relay, the main junction, and then half the fuse box is hot from the main junction. The other half of the fuses are only hot when the key is switched to run or accessory.