Ditto on whats been said on the block # (
oil pan rail near bellhousing). Also mine is a shelby assembled engine so it has 2 numbers, one CSX088 for the block and CSX125 for the engine. So I have both of those #s on the back though the 125 # is not stamped it is written with an engraving tool. Also I had my pan off and each of the caps has the block # and each of the pistons (underside) has the engine # on them. They really label everything!