Volt /Ammeter at odds ??

Lets look at the diagram again.
The ignition and alternator's rotor use about 4 amps together.
Turn on the headlights and there's another 9 - 11 amps needed.
Maybe the alternator supplies some of that, but your ammeter shows the rest is coming from the battery.
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The only explanation for that is high resistance in the alternator output wire.
Your bulkheads connector shows repair and possible heat damage, so that's the most likely first culprit.
There may be more.

Get a '68 shop manual. You'll see where the wiring diagrams the schematics here were based on. It will also have all the cavities in the bulkhead connector for your car, and the correct wire colors.
I don't show the connector cavities in the schematics here because every year and model has slight differences. Wire colors, switch connectors, and other details also may be a little different. Differences of no importance for discussion but you need the exact color, size, etc when tracing on the car.
For example I think in '68 wire from the main splice to the ignition switch got red insulation. Anyway, tThe last thing we want to do is unwrap all the harnesses just to follow a wire.