Your wrong, it was put into place for "legal reasons". It wasn't just Chevrolet it was across the board, all GM brands. And it didn't just cover engines, it covered transmissions too. Exactly :
"The attached letter from F.J. Welsh outlines the basic requirements to be fullfilled by the source plants supplying engines or transmissions assemblies and/or components for serive which must be identified to comply with legal requirements". End quote.
From J. Semenik to various at engine plants dated August 3rd, 1967
" This has reference to placing identification numbers on passenger 1968 and later model replacement engines, partial engines, fitted cylinder cases, transmission assemblies and transmission cases to comply with State of Georgia law which becomes effective with the start of the 1968 model year'.
this was an inter office memo from F.J. Welsh, Central Office to Mr. J. Semenik, Engineering Center dated August 1st, 1968
I don't know where you got your information, mine comes from inter-office memo's between Chevrolet engineering and the Tonawanda engine plant. I don't think I'm right, I know I'm right according to the paperwork I have in my hands. And I only wrote a small portion of what these memo's say. I said it was federal, I rememered it was a law, forgot it was State of georgia. I believe this was required by other states if not the feds further down the road.
Of course because they HAD to do it, and keep records those records could also have been used for other purposes. But the identifying code went on everything, not just warrentee parts.
[Underlining fixed by Kurt]