Quit trying to overthink this.
Where the ballast was, there should be 2 feed wires- one blue, one brown (confirm the colors in your FSM, I'm using the colors normally associated with A bodies; but yours should be similar).
These are your IGN1 and IGN2 wires. (green circle/arrow)
View attachment 1716257767
Remove the ballast connectors and strip the ends of the wires, and connect them together- crimp, solder, whatever. Then connect that to your proposed relay trigger wire. Done.
DON'T eliminate any of the blue wire or connections/splices to it, as this wire also feeds other circuits to the alternator, voltage regulator, electric choke, etc.