Last year I acquired a plane with an overhauled IO-520 from America's Aircraft Engines with about 260 hours SMOH, which was from ten years ago. A very nice binder, provided by America's Aircraft Engines, documented many of the details of the overhaul. I decided to call them just to get an impression on how competent they seemed (as best one can determine this from a phone call). I was very impressed that they had the original work order and went to the trouble to scan and email all of the documents to me. Perhaps more important, after 10 years and 300+ hours no oil leaks, doesn't use any oil, and compressions are high 70s.