Interesting note! In the last few days I have learned, through GM, that prior to 1972 most, if not all, of the records from the GM engine manufacturing plants were destroyed on a regular basis as they did not have room to store them. GM corporate was not required to do so and they generally did not. Therefore, this begs the questions, where did the plethora of information come from for engine stamping numbers and how reliable are these sources without GM's ability to confirm? Additionally, read an accounting of GM engine plant operation it was such that sometimes they would just put blocks in the assembly line randomly regardless of the casting numbers and engine id #s. The engine serial/VIN#s were stamped at the vehicle assembly plants as they were installed into the chassis, again not always mindful of what casting or engine id#s were on the block. Therefore, unless anyone were fortunate enough to match an owners specific car to the serial/VIN combination and researched the actual vehicles installed original equipment a person could not identify, without at least some doubt, what those blocks were used in unless some other organization/persons recorded this info??? the question marks are tri-purpose; 1 my conclusions are just logical thoughts, to express my confusion, and to display my extreme curiousity with this process!