I called my machinest yesterday and he said to come down, he wanted to show me something. I came down there today and he explained that he was putting the new pistons with the new rings in the bore and when he mic checked # 6 it was .010 to large, and it turns out that # 8 was also .010 overbore and there was a stamp that said .010 GM on the top of the oil gallary next to numbers 6 and 8. He said hes never heard of that, all the rest of the cylinders were std bore. He had to sleeve the cylinders and make them std bore again. Is this a good way to fix things? has anyone ever heard of a block like this? To my knowledge it is completely stock from GM. the stamp has GM on it. It is a Hencho en Mexico Block as well.