I recently found this in the first 350 i built when i was in high school.... we’ve had this engine in several vehicles over the past 25 years. It was making noise that almost sounded like a rod knock but was more high pitched. I could have sworn the noise was coming from the back of the engine or bellhousing. After we didnt find anything loose or out of place there, we just kept taking things apart until we found this. It stayed together and never came apart in the bore. Dont have a picture of the cylinder wall, but its fine, could probably just replace one piston and rings and be done with it.