Cosmoline wore off quite quickly, I doubt you'd find any on most examples, normally you just see bare steel and rust. What you can sometimes see is a line near the ends where the metal is in better or worse condition indicating that some areas had protection for a while and others did not. *Also, don't mistake any inspection paint blotches you see as part of an overall coverage, the torsion bar adjusters are commonly blotched with paint, some of it was black.

Chrysler had multiple vendors for most parts, not all vendors did things the same way in meeting the specs on the print, one might have used Cosmoline while another used paint to offer the required temporary rust protection. Then there were different vendors for different plants (and Lynch Road and Los Angeles are known for having some unique parts sources) There could have been a change mandated by Chrysler to paint them black in later years.

That said, MANY replacement parts were painted black, likely because it offered better rust protection and made for an easier to handle part.

All of my NOS examples have been Cosmolined, and most had part label tags dated in the early to mid 1970's, after 1971 production ended.

So yes, it's possible yours were black. When faced with (any) detail that is out of the accepted "norm" it's always a good idea to document as many unmolested examples as possible to support your case.