67 Barracuda Heavy Electric Load

DallasMan2000 said
Here is the voltage gage with electric radiator fan running with headlights off, then second pic is with electric radiator fan running and with headlights on.

No its not. That is amps to or from the battery IF AND ONLY IF the fan is wired to the alternator side of the engine side of the meter.
The link I provided in post 11 will illustrate this.

DallasMan2000 said
Is a standard digital multimeter like this capable of measuring the alternator amperage?

many, but not all, multimeters can meaure as much as 10 amperes current briefly. The one you have can not. It probably could be used with an inductive clamp that measures current. (see the second link in post 11 for info on one such clamp). The symbols on this meter's selection represent

Ohms (resistance) Voltage DC (Potential difference)
Continuity Voltage AC

DallasMan2000 said
The wiring harness was replaced a few years ago. I said it is “factory” because my understanding is that the replacement wiring is “factory like”. I bought the car last summer and it has lots of upgrades and I am sketchy about many of the details. The Hanmetek meter I purchased on Amazon reads DC volts but it might also read amps - not sure about this.

Lets start at the basics. Voltage is like pressure in a pipe. With everything off, the battery voltage is like the water pressure in your house with all the valves closed.
Current is electrons moving. Think of current in a river. With everything off, no current flows out of the battery. Turn something on like the lights, or the fans and current flows to those items and back to the battery's ground post.

When the engine is running, the alternator provides a higher voltage source of power then the battery. Measure voltage at the alternator output with the engine running and it should be around 14 Volts. This is why the alternator charges the battery and why power for running the car comes from the alternator when everything is working right.
Again, please look at the links provided in post 11.

DallasMan2000 said
The previous owner gave me the clutch fan that he removed. I would rather stick with the electric fan if possible. The new wiring still goes through the firewall with “factory like” connectors. See pic below.

Installing the clutch and mechanical fan is actually the simple answer. Adding electric fans, especially ones that may draw near 10 amps, really requires a rework of the factory wiring strategy. And the advantage of the electric fan is ? what ? for all this effort? A potential disadvantage is more restrictive airflow through the radiator than any of the factory options.
You don't have to believe me. Search through the heating and cooling forum and see the number of people who have struggled with the electric fans their shrouds. (Note the factory blades are 17 to 18" in diameter.) Can it be done? Of course. But it will likely be a project, not a plug and chug.