- 1970–1972 Confirmed
footnote-flagged in source (Canada/export, build-sheet/tag-only, documentation-only, or package base engine not reported as an option — see chevellestuff legend)
C56 Confirmed
Also described as Upper level ventilation
Documented applications
- 1963–70s (varies) Confirmed
This page aggregates every documented appearance of C56 in the Chevrolet reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.