I think car engines have a long life history in aviation of just about exactly zero.
I know this has been done to death here many times but a typical car engine runs at 10-20% power most of the time. A typical 2000cc engine (i.e. assuming top speed of 120mph; my 1987 Celica would do 130) doing 70mph is running at about 30-40% power.
Anybody trying to run them at 65% or g0d forbid 75% power finds they fall apart fast. On serious rally cars, they change engines almost as often as they change tyres (but you don't see that on the TV coverage).
OK, one can "do a Thielert" and beef up the bits which you think are most likely to fall apart, but this is still a long way from "most" engines (well, non turbo ones, anyway
which is why I never bought a TB21) making a 2000hr TBO without any issues.
Back to mags, in the 1970s I used to make electronic ignition systems for motorbikes. These initially used the contact points (which would last for ever, due to the elimination of arcing) and later I did a magnetic pickup. I don't think there was any real obvious failure mechanism, and one could massively over-engineer the bits which were most stressed (the capacitor, and the semiconductors) but I would not trust Lyco or Conti to get somebody competent on the job, even though the car makers have pretty well sussed this in the intervening 30+ years.
Mags are damn expensive. I have just paid $2.5k for a factory overhauled D3000 mag, and that is just the mag, not the lid with the ignition harness. That is plenty of a budget for an electronic ignition and a distributor.