[dlv4540]

I believe it is a mistamp from the factory and should be ID but was stamped as 4D. I can send a picture to your email address if you provide it. I have a hard time posting pictures on this site. I figured if someone wants to use it for a corvette they can always deck the block and get rid of the stampings. It is a real 4 bolt block by the reliefs cut out of the top of the cylinders along with the larger holes down by the oil filter.