"For posterity - apparently, the coil supplied with the Magna-Spark kit is too hot for the pickup module supplied in the distributor."
Well, at least that one might be suspect, but we don't know enough to suspect all of them. I've got two seasons on mine and it seems fine (so far!)
Something else to consider is the voltage at the + side of the coil when the engine is at, say, 3,000 rpm - Is the alternator cranking out more than 14.5 volts? if it's more than 14.7 Volts that may be damaging the module, too.
Be a bit careful when using an old-school Ballast Resistor on an electronic ignition module. It may not be the insurance you're seeking.
The way that they're intended to work is that they go on the +12 volt side of the coil and when they're cold they have very little resistance and provide full 12 volts to the coil. The intent is to provide a "hot spark" when starting a cold engine to make it start easier/faster.
As the engine is running and current is flowing through the Ballast resistor, it heats up and the resistance increases to a point where a "cruising voltage" is reached (somewhere around 10 volts) and it remains at that resistance/voltage until the engine is turned off, current no longer flows and the resistor cools off.
You'll still be hitting the coil and the module with full 12 volts during startup and for a minute or more afterward.
GM used Ballast resistors for quite a few years, mostly on trucks but on some cars, too, for quicker starts. They required a coil that worked at 10 volts and the ballast would provide that while cruising. That also meant that you were running the coil with a heavier voltage during start-up. Ballasts were blamed for pitting points and burning out coils from over-voltage through them, but often it was that the condenser was going bad and not bleeding off enough of the charge. I saw quite a few condensers go bad on Chevy 350 engines by pitting the points in one direction or the other, telling you the condenser capacitance had changed from optimum. If I bought Echlin or genuine Delco condensers they seemed to last a lot longer. I can't remember swapping out a bad Ballast Resistor, but I might have, sometime.