Yes. The book diagrams are not that clear on these options. We'll have to figure out what is actually on Mark's car.
Post 1. Back of ammeter photos show two wires at the black wire junction.
According to the shop manual, there should be three with 60 amp alternator and the rear window defroster grid.
Side note. Looks like the insulation is cracked and the connections are not exactly clean. Next time in there ( with the battery disconnected, remove clean, and reinstall.) Unless you see serious damage, a dab of liquid electrical tape should close up the insulation damage.
Post 18. First photo shows 3 wires battery wires at relay junction.
View attachment 1716023128
One is from the battery.
Can you see where the second red wire goes? or does it gointo the wrapped harness?
The diagrams show the fuseable link is the line going to the ammeter through the grommet.
Does this fusible link connect to a red wire going to the grommet. If not, where does it go?
(it would be a good idea to clean these connections too. again disconnect the battery first.)
Same post, photos show a heavy red wire coming out of the harness with a round white connector.
Where does it connect to? A fusible link?
View attachment 1716023130
Finally there are two black wires coming out of the grommet.
One comes from the alternator output.
What does the other connect to?
View attachment 1716023131
This is the diagram so far.
With the questions above answered and some more photos probably can figure it out.
View attachment 1716023132
Explanation of the wire codes.
A is Battery related. A1 is a branch and A1A is the first segment. 10 R is 10 gage Red insulation.
R is alternator related. R6 is alternator output. R3 is control of the rotor power.
J is Ignition related, although by 1974 that includes the feed into the key switch, power to alternator, and the electric choke.
J1 is power to key switch, J2 is run.