Thanks for the information. So there is such a thing as a middle block but only one ever made. I guess that is why I have never heard of it since there has only been one made. I know size has something to do with it but being there are small blocks from .10 to .18 and big blocks from (not sure where they start and end as it is an ever changing thing) .20 to over .30. But does mounting bolt pattern have a lot to do with where it is a big block or a small block? If so I am guessing then the only middle block is different from either one? [8D]