1974 Brain Box saves the day.

Just read through the post. Transistors were as good as it got back in the 1970's. I designed a small engine ignition controller about a year and a half ago using an IGBT instead of transistor. In fact, it (GB14C40L) is specifically designed to drive ignition coils. The ballast resistor helps compensate for dwell exceeding the inductive saturation point of the coil; when it becomes a dead short. I used a PIC microprocessor to control a fixed dwell. I pulsed the coil on the bench measured the time constant with a scope (2.1 ms). Converting a mag-style signal (like Chrysler electronic distributors generate) to a usable digital signal was done with a Maxim MAX9924 VR Signal conditioner.

Believe it or not, one of the major causes of any controller to fail is old capacitors. Even the '90s era Mopars have ECUs failing due to dead capacitors (I've replaced a few). It's possible that when the cap fails, it takes other components with it; parts it was protecting when it was working.

Someone mentioned designing a replacement for the old Mopar Electronic Ignition Controllers. I would probably use the new Silicon Carbide (SiC) type IGBTs, as they have stupid low internal resistance. This means they generate very little heat! They switch in 2-3 nano seconds, and start at about 650 volt ratings and go up from there. Spend a few more bucks and use Gallium Nitrate (GaN, better than even SiC) switches.

When you look at what the OEMs are doing to fire coils (and even injectors), it's worlds apart from the '70s Gold Standard.