Adam,
This may not apply to your immediate problem, but may bite you again in the near future: I notice you mount the coil to the engine.
If you want the coil to be reliable, get this one: MSD Blaster High-Vibration. It is epoxy-filled and will last much longer when bolted to the engine. The heat combined with the vibration of the engine will kill a normal
oil-filled coil fairly quickly.
Alternatively, the coil can be moved to a structural location such as an inner fender or frame brace to isolate it from the engine a bit.
Just a heads-up,
Tom
PS: Way back I had a similar problem. It turned out to be a bad butt splice connector in a wire going to the coil. At first it was intermittent, later had to trailer the car home. Took some real detective work to find it as it was located under a fender in an enclosed space. The clue was no voltage at the coil. Maybe you could connect a voltmeter to the hot side of the coil and wiggle wires here and there while watching (or your assistant watches) the voltage.