Could the end gap have been to tight and broke the ring lands and the top of the piston?
As far as my sons cost Call him and get a price. I was down there today to baby sit his girls with my wife. He was neutral balancing a 360. I gave him all my 340 blocks but I don't know if any are for sale. He is a worse hoarder than I am.
But he does many sleeves in engines of all types.