Overall there were quite a few '74 Z28s built, and the 2nd generation Camaro forum NastyZ28 shows production count at 13,802. However the one you found it pretty unusual with the Lime Yellow paint (Code 40) and a 4-speed.
https://nastyz28.com/camaro/camaro74.html
As others have mentioned it's pretty remarkable how original the entire car is, especially the engine bay, retaining the original air cleaner, exhaust manifolds, smog, etc. It might be a bear to restore but it would be one cool ride when it's done!