What FF said, plus...
Though a calendar requirement for overhaul may not be applicable, you also don't want an engine which has sat idle for long periods. If the engine was built in the '70's, has been overhauled once or twice since, and used fairly regularly 50 hours or so a year, it's probably a better choice. If it has sat idle for months since the last overhaul (otherwise than having been properly preserved), be cautious - corrosion.
Cylinders should be considered long period consumable. They could need repair/replacement during the whole engine overhaul interval. For my experience, if one cylinder needs work approaching 1000 hours in service, you may as well have them all done.
For your reference, I bought my C150M in 1987, with 1700 hours since the second overhaul (so very close to the third), god a deal, 'run out engine. I flew it and checked it and the engine was good, the owner had taken care of it, and flown regularly. That was just when Canada was changing to engine on condition (my buying strategy). I put the engine on that program. I flew five hundred hours or so, overhauled all four cylinders, and the accessories, looked in to check the cam lobes, and kept flying. At 3600 hours since overhaul, I found some metal in the oil filter, so I disassembled it for inspection. The metal had come from the alternator drive, so non critical. The only defect in the engine itself was that one crankshaft bearing surface was 0.0008" undersize on the power side. I had the crankshaft ground ten under, MPI'd and reinstalled it. I also had the cylinders and accessories all overhauled too. The engine shop told me that for another $1000 in replacement parts (mostly valves), the engine could be recorded as "overhauled" (to zero time) rather than "repaired", so I did that.
I've flown it another 1000 hours since that overhaul, doing accessories as required along the way. I have just overhauled the cylinders again, and it runs very nicely. But frequent use, regular oil changes and maintenance are key to keeping your engine in good shape - rather than numbers in a log book!