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.

It occurred to me today as I was reinstalling the dashboard (after 17 years) that because I have completely separate wiring for the Vintage Air HVAC system, I mighty just take the power intended for the OEM heater/blower and use that instead of finding a KEY-ON wire. Yes, I know that circuit is activated in the ig-switch's ACC position but because I don't have adolescents who will want to listen to the radio when the car is not running, that might be a good option.

I found a 12v switched wire here under the blue tape. Used it for my fan controller that I put on the firewall. I did do the headlight relays where I removed the voltage regulator when I did the internally regulated alternator.

I may have inadvertently covered up that wire when I re-wrapped all my harnesses several years ago (what a FUN time that was).

In any case, I've decided to go with a fuse tap in the main fuse box on the 20 A FLASHER fuse, which is the only circuit in the box that is KEY-ON activated. Will use a 10 A fuse for my Retrosound Motor 4 radio, Vintage Air HVAC controller and Valentine One radar detector.

Frankly, until yesterday I didn't know such a thing as a fuse tap existed. Ran across it when searching online how to hard-wire my radar detector. Really happy now that I swapped the OEM fuse box for an ATO-style one from Motorsport Auto.

What a clever little piece! Never heard of that either