Looking at those pics reminded me some of my '61 348 that morphed into a 434. When I got it home, I took it apart. Five pistons came out ok. Cylinders looked fine. One piston I struggled a little with. Cylinder was slightly pitted/rusted. Seventh piston and cylinder worse. The last piston I believe was #5 cylinder, this piston was frozen very well in the cylinder. I tried everything and thought about cutting it out. I then used a block of wood and heavier 8 lb. sledge hammer as a last attempt. I whacked it hard a few times. So much so, I thought the engine might come off the engine stand. The piston came flying out and I inspected the cylinder. What a mess with rust and serious pitting. I thought for sure I bought a boat anchor. Took it to the machine shop thinking from there to the junkyard. I was surprised. The machinist said he would take care of it and did. No sleeve. Guess the overbore took care of it. I was very pleased to say the least. The motor ran real well in my '56 gasser. I don;t think I had nearly as much pitting that I see in those pics. Block surfaces were very good. Sad that block has so many issues, Carmine.