As I mentioned, it was random in 1970, some had them, some did not, early cars less likely, later cars more likely but not definative. They used parts with no real inventory control back then, no "first in first out" as we commonly see today, it was not a mandated 1970 model year change, just a part that changed during 1970 production. Same applies to other 1970 sheet metal stampings like inner fenders and hoods with and without crush zones.