whereas automotive applications rarely experience failures?
I had an XR3i in the 1980s, and the gearbox shredded itself, gradually over about 30 miles, through the disintegration of a bearing around the tacho takeoff shaft, which took off the teeth one by one... by the time I got home, only the 4th gear was working.
Then I had a total loss of coolant in a Toyota Celica (suprisingly).
And two alternators go in another (imported) Toyota, to date.
Countless cracked aircon compressors in the Celica too - an experience reported by aircraft aircon system owners too.
I have flown about 1000 airborne hours, which is perhaps 1/2 of my total car / motorbike mileage, yet I have not had a single mechanical failure on the aircraft, whose engine sits there at 65% power all the time, and best part of 100% power for some minutes after each takeoff.
On the basis of the above admittedly small set of data points, I don't think I would swap my IO540 for any car engine.