There is good information and some not so good information in this thread.

Barry's recommendation about the dimmer switch is spot on. Many Mopes have had that issue.

Robert is also correct.
Bulkhead connectors are also a common Mope issue. The Packard connectors in the bulkhead are only rated at 40 amps when brand new. Add a bit of corrosion, 50 years of time and that shiny brass connector that came from the factory is heating to an alarming degree.

The splices in the harness are also alarming. Wire nuts and splices can make for "ohmic" connections meaning they also can heat up and cause flaming issues. There should be no splices in the heavy gauge wires such as the alternator post, headlight wires and fusible link.

One piece of bad information is on Halogen headlights. They are much more efficient that the tungsten ones the cars came with. Halogens put out more lumens per watt and therefore draw less current than the old ones did. That is why the industry went to them.

All in all, you have a lot of trouble shooting ahead of you. Go for the easy stuff first but do not skip anything, even if you find the problem, there could be something else lurking another wire bundle.

Craig