One piece at a time.
1)
Progress,
In a wire diagram, it shows the brown wire is connected to the c222 connection via The B connector. Is that my missing link?
The connector you circled is not the C-222 connector in the schematic in post #282.
It is connector C-218 in post #282.
The connector you circled is "B". This is the red connector in post #283 photo.
The Ford engine harness plugs into it, and connects the oil pressure sensor, temp sensor, and coil power leads. The oil and temp wires go to the Ford instrument cluster.
Not wanting to go back thru 15 pages of posts, remind us what you are using to control this LS engine (points, computer)?
2)
On to starter issues.
When the starter relay clunks, you should get 12v on large gauge wire leading to starter.
On a Ford starter, the one wire connection supplies 12v to the starter engaging it with flywheel, and spining the starter motor.
The last time I worked on a GM starter there were two wires connected to the starter.
The large gauge wire supplied CONSTANT 12v to starter.
There was also a small guage wire that energized the solenoid causing the starter to engage the flywheel, AND completing the circuit from the large gauge wire to the starter motor, causing it to spin.
3)
When I turned the key to start the motor, all systems seem to short out and restart. See attached video.
Looking at the video you posted, when turning the key to start, every thing went dark.
This may not be what you called a short out.
All your accesories work when the key is in ON or ACC positions. This is as expected and good.
A known issue with Ford ignition switches (50 years old, or new out of box) is when the switch is turned to START it disconnects the ON/ACC circuits, and kills all power to everything, but the starter circuit.