Thanks Rick. I am using the
oil filled high vibration coil, #8222 and, yes, it is mounted to the head in the traditional way. When I called MSD I first spoke with a technician and explained where and how it is mounted (with an MSD bracket designed to bolt to the head). I specifically asked him about the heat in that location and he said the coil can handle that heat. That said, heat being the reason it failed as you described above still makes more sense to me. Regardless, I now have a spare MSD AL6, distributor cap, rotor and coil (as soon as their replacement arrives) to carry around in case one of these fails. Considering getting a spare magnetic pick-up as well. May be overkill, but it is so easy to replace any of these things roadside, I'd rather do that than call a tow truck.
As a preventive measure, I'm thinking of moving the coil out away from the head with some thick phenolic spacers. It is in an area of good air flow so getting it away from the head even another 1/2 inch would probably keep it cooler.
Kevin