Finding switched 12 volt source

There is only one (two) switched ignition sources under the hood. Period. I said (two) because that refers to the cranking coil bypass circuit

IGN1, usually dark blue comes out of the bulkhead and branches off, depending on year, to feed the ballast, the VR, the alternator field, electric choke "if used" and some smog doo dads on some years. IT IS NOT FUSED OR PROTECTED in any way

IGN1 is hot ONLY in run IT GOES DEAD in cranking

The only source during cranking is IGN2 which is hot ONLY in cranking. It is NOT the same as the yellow "start" wire. Normally brown, it connects to the coil+ side of the ballast.

Basically you need to splice all of the ballast wires together and run the original coil+ wire off to your new ignition system power connection.

That car has a 4 pin ballast. If you are going to strip out the old harness parts, you can eliminate the wire that feeds to the "box" from the ballast and the 12V wire going to the box, as well, of course the two trigger wires and the old coil NEG wire

Be sure you don't end up dropping a wire out that leaves the VR or alternator field unpowered