More deep thought here (LOL)! As the id numbers on the block I have possession of do not conform to the standard stamping process identification lists available - ie. odd serial number letter combination. I have come up with a logical possibility, among many, that due to the strange prefix of C by itself and not a 1 or CE that this may be a block that was produced to be installed sometime after April 1968 in a Canadian vehicle. Can't be newer than 1972 as Feds passed laws making the automotive manufacturers standardize, and maintain these records.The stamped date code confirms it is either a 1968 or 1978 engine block and policy and law says it cannot be a 78 piece. The engine id being V0516TDB it narrows down the production facility and a May 16th date,showing either a late 1968 or 1969 vehicle? The TDB is where much more confusion comes in as GM didn't use the 3 letter suffix until 1970 but it would denote, from what I can find, makes it either a 302, 307, 327, or 350. This is definitely not a 307 as no 307 4 bolt blocks were ever produced nor was the 3970010 block used in the 307. That leaves 302, 327,or 350. Also, addressing what is known about Chevrolet small blocks it is extremely doubtful that it is a 4 bolt 327, because as far as I can find out they are only a myth and if produced they were most likely were found in Canadian trucks. Would make sense with the "T" designation in the engine code that it was destined to be installed in a truck. Allowing for a Canadian installation, I can understand the differences in the serial/VIN number format. Did they use a different suffix format in the engine code as well? I doubt it. So, is the suffix for this block actually just DB and the preceding T mean something else? I don't know as I can't find any reference for a DB suffix for a small block! Therefore, I can only conclude that this block is either a 350 or 302 4 bolt main engine block. Now back to the serial/vin code- what does the "Z" designation? Can't find any reference to that either. So, I can't reliably identify this engine block. Another thought is did someone change/stamp the engine id code to match their car? That is a possibility but once again doubtful as when I acquired the block it was standard bore and I can't see anyone doing a matching numbers car/truck without remanufacturing the engine. That just doesn't make sense to me. As far as it being a 302 block who knows? Like I said the numbers don't conform to what I've learned anywhere about the Z/28 Camaros. However, with the questionable numbers and sequences as they appear on this block and GMs inconsistancies in identification processes prior to 1972 and possibility of a Canadian installation it still doesn't rule out the 302 block. Any Canadian afficianados out there? While my wallet would love if it turned out to be a 302, I am still very, very doubtful that it is such a find. However, as a retired former owner of a jobber automotive machine shop it is possible as thousands and thousands and thousands of these engines passed through my shop. My present conclusion is the only way to know would be to find the vehicle that has the matching VIN.