Newby question here? Can't new rings be installed in old pistons? I'd recreate a honing pattern (for better surface oiling) in the cylinder wall, and just call it good? Don't replace parts that aren't broken kind-of-approach on antique or non-resotored vehicles. Unless the bores have enough...
The valve clearances were checked for wiggle, when closed, on a failed cylinder?
Think about it, you can't get horrible leak-down results without other signs of catastrophe, or long-term wear. Does the PCV valve / hose connected to intake manifold look like La Brea Tar Pits?