If the motor has overheated, you should see signs of overheating such as discolored paint on the cylinder head, and relatively loose cylinder head bolts. A bad overheat will produce scored pistons and brittle heat weakened rings. It doesn’t sound like this motor experienced a bad overheat. If the motor hasn’t overheated badly, then the rings may be salvageable.
At this point, it may be prudent to take a very close look at the cylinder head. Inspect the head for any tiny cracks, or imperfections. If it passes inspection, resurface the mating surface by lapping it on a plate of glass, or a large, polished floor tile. While you’re at it, inspect the mating surface of the block also. The block can also be lapped if it has gouges or is not flat.
I believe the standard rings for that motor were used for many years going back to the 1940’s, and into the 1960’s. There are older part numbers that may help with your search. Try PN 378432 or 041333.
Improvise-Adapt-Overcome
