I don't know where you guys find these detailed diagrams but I'm sure glad that you have and share them.

3 hours ago, Seppi72 said:

I don't know where you guys find these detailed diagrams but I'm sure glad that you have and share them.

Reading the factory service manuals.

If you haven’t done so already, download the FSM for your car off this site.

I have the 1972 body and engine FSMs, which I've had since 1972 (purchased from BRE and now installed in 3-ring binders with each page lovingly protected), but the body one doesn't have anywhere near the level of detail as some of the illustrations that have been presented in this thread. I'll check out what's on the site.

7 hours ago, Zed Head said:

What would be the reason for avoiding the coil power supply if a relay is used?

Just a (probably unnecessary) precaution. It's the same wire that runs to the voltage regulator, but it probably has more electrical noise the closer you get to the coil.

Even though it's the same wire, there's some filtering that will occur as a result of the natural inductance and capacitance that will exist in the length of wire over on the other side of the engine compartment. I wouldn't be surprised if the voltage dips more (when the points are closed) over by the coil than it would over at the regulator. And the voltage will blip higher when the points open closer to the coil than by the regulator. Even though it's the same wire.

Again, probably doesn't really matter if you're just hanging a relay on it, but if given a choice, I'd tap in as far from the coil as would be convenient.