MAD ELECTRICAL?

My experience is limited to 60’s a bodies, so there may be others on the forum that can speak to this better. In general, however, I don’t see an issue with what you describe except for the lack of a fusible link. The feed wire from the starter relay (battery supply) should go through a fusible link, then to the plus side of the ampmeter. All the loads and the alternator come off the black side of the ampmeter. This way it measures all the current going in or out of the battery.

The white connector in the picture looks like a fusible link connector. Is that what it is?

The closer the fusible link is to the battery, the more protection you have.