I can't imagine any reason for an assembly plant to date-stamp any component; my Production Engineering Group supplied the G.T. Schmidt VIN derivative-stamping tooling (for the body and for the block pad and the transmission) to all Chevrolet assembly plants, but we never supplied any tooling for date-stamping. I'd guess those date stamps were applied at the subframe manufacturing source for traceability. I don't recall who made the "F"-body subframes, but most Chevrolet frames were made by Dana, A.O. Smith, Parish, and Chevrolet-Bristol Road Stamping in Flint.
