Non A-body mopar question

Sometimes mechanical things just fail. Did you put all 200k miles on your 68 Dart? If so and there was no one event you recall that would have severely stressed it over the last 57 years then chalk it up to metal flaw.
Nope, 71k Original miles car. Engine ans trans still in fantastic shape. Bought it off the original owner. Guess it's just one of those things