Squareback Connection to Electronic VR

Light gray wire with stripe goes to electronic ignition
Thats a part of the connector pigtail. That and the Voltage Regulator's pigtail will have to be spliced into.
For the rest of it, I'd start over and replace the Run circuit, and if the alternator output wire is compromised, repair or replace that. That R6 wire if it needs replacing must be 12 gage, have really good crimps, and be routed so its secure and protected.
Normally following the factory routing provides a good path and mounting locations, but it will depend somewhat on where the electronic ignition and new voltage regulator are placed.

My recollection is that you have packard terminals and crimpers.
These are the five wires on the ignition and regulator circuit that I'd re-install.
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To connect the four wires at the ballast resistor, use one piggyback and make pair the wires on the female terminals.

Piggyback slides onto the ballast resistor.
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Pair wires to use the terminal as a junction.
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That's a way to joint 4 wires together without a big splice.
And if you need to trouble shoot, its easy to probe or disconnect.