Charlie, the factory short blocks came with the first 3 numbers denoting the displacement already stamped and the mechanic finished it out. However, if a used engine was installed, the boss was ground smooth and numbers were stamped on. If you look at the numbers and the first 3 look professional, it could be a factory short block. If they all look professional, its probably the original engine. If they all look like I did it, its probably a used engine and can be anything. The only way of knowing for sure then is like they used to do at the old Double Eagle strip in San Antonio..Make you pull a head. Maybe you have a 270, beings it runs so good. But a good 248 is a big improvement over a 228.
