From Novasource.com:
"1972- optional package: because 1972 is the first year the original engine is coded in the VIN, you can tell a real SS by the engine code. All 1972 Novas came with the L48 350 4-bbl engine. The L48 was only available in the SS so if the 5th digit of the VIN is a K, the original engine is a L48 and it must be a real SS. BTW, like 1969-71 Novas, all 1972 Super Sports had power front disc brakes."
