Steve. I don't know where 273Dart has been. Seemed like he was helping you.
I've not followed your threads and posts in any detail. I know you've made several changes. My suggestion for a diagram is to start with the '67 ignition charging diagram. Take the one I've posted on my website and here.
Then print it or open it in MSPaint, IRFAN or whatever drawing software you like.
Mark it up precisely with each of the wires and items you've added.
By precisely I mean to have the wire connections at their actual locations. If its a splice, show it as a splice (solid circle), if it joins at a terminal, show it there.
The first iteration will be a bit messy. That's fine. Move things around (redraw if on paper) so its clearer to you. You probably don't need starter (yellow) for this particular problem, so you can delete things that for more room.
Once you have it the way you like, make copies so you can mark the voltage readings right on it. Then you should be able to see where the voltage drop is relative to current flow.
View attachment 1715227363