John Parker, one of the veteran engine mechanics in the club, had over 250,000 miles on the one in his 1948 Kaiser Special in the late 1970's.
The actual life of an engine starts with the foundry where the major castings are made (block, head, exhaust/intake manifolds, etc) the plant where the engine is assembled and transportation of components and engine to the car assembly plant. Having been an engineer in the engine field for around 5 years or so in my career, I know that the closer to meeting nominal dimensions for various parts of the engine is significant as to how it will run out over time.
The life expectancy of the 226 like any other old car engine of the period is, as Jim said, dependent in large measure on how the engine was cared for including how religious the oil change, timing, and other general servicing was performed per the manufacturers specifications. There are still people finding cars that have not run for over 30 years but, with a bit of TLC in set-up and use of things like Marvel Mystery Oil in the cylinders to open up oxidation areas (if they exist), it has been found that the engines will turn over and start if the coil, distributor, etc are still in working condition. You will see some of these events on YouTube and other social media.
Of course there are some cars found with less than 30,000 apparently documented original miles on them that have blocks that deteriorated over time and cannot be rebuilt.
