The coil I was using was a Pertronix Flamethrower, which specifically states that it wants a full 12v without the ballast wire.
I doubt it died from overheating as it has been in my car for five or more years now! It has definitely seen many worse drives. However, I'm paranoid that the new Holley system managed to kill it somehow. But even that doesn't really make sense since I had driven 580 miles on the same day before it died. I'm hoping it just gave up.
Ummm, note the instruction sheet where it says to NOT remove the ballast or resistance wire if the primary resistance is lower than specified. With the ballast resistor/resistance wire the primary resistance should be at or near 1.5 ohms. Without the resistance wire your primary resistance is going to be at or near 0.1 ohm.
I don't think Pertronix is very clear about this value NOT including the internal resistance of the coil itself. The total primary circuit resistance, measured from the ignition switch "C" terminal to ground, with the points or trigger closed (coil being charged) should be around 3.0 ohms.