Now one more thing you need to consider, is who ever built that, looks like the were not "as skilled" as they should be, so I would be very cautious of the actual finished bore size, because those pistons would have required more piston to wall clearance than a modern forged piston, so you may not be able to just drop in a different piston. And based on the quality of work, I seriously doubt they had the equipment of skill to make the bores round and straight. If it were sent to me, I'd probably plate hone it to .040, new icon pistons and know it was right. That's my free 2cents