1969 Z28 ID Help

[Als 70 L78 Nova]

Looking at a 1969 Z28. I asked for a photo of the engine pad stampings and only received a photo of the assembly plant, build date and the DZ designation. I then asked for a photo of the Vin number stamped on the pad and received the following response: "Most of the X77 cars I have seen do not have the VIN on the engine pad." I am not saying this is wrong, I simply don't know. I thought that it was a government mandate that all cars after 1968 had the Vin stamped somewhere on the block. Could someone please weigh in on this? Thanks