When you needed a new Ford flathead engine back in the day, Sears kept Allstate rebuilt motors in stock. You would pull in, and they would swap out your old engine for a new one. This was also done by Ford dealers and Western Auto. As well as a number of other lesser known companies. Which furthers the chances, you do not have the original motor. Because back then, no one cared until the 60s. They just wanted to get back on the road. This reduced rebuild time from a few weeks, down to a few days or less.