Haven't had much luck with this search but hopefully someone here might be knowledgeable about the engine ID numbers and what they can tell you. My '04 D2 has a replacement 4.6 block that didn't have documentation as to where it originated; the story was it was a crate replacement in a customer's Defender, who had it removed after a short time when he went to a TDI. Block looked new and runs great so I have no reason to question that part. I've been trying to track down the origins, however, and all I have is the engine serial number (50M107D2) near the driver's side exhaust manifold. There might be a digit before the 5 but I can't tell for sure. I inquired with AB and they said it's not one of theirs. Any ideas? It's just a curiosity thing really. Thanks!