That being said, the ribbed or ''spine'' deck lid showed up on the late '71 cars as well as the bumper jack slots that all of the '72s had.
I had a late build '71 Duster (07/ 23/ 71) that had the ribbed trunk lid w/cut outs for the spoiler and bumper jack slots. It was an all original slant 6 car including paint if that matters.
My '71 Demon Sizzler has a flat trunk lid with spoiler cut outs and it's build date is late Feb of '71, and it's all original. It has no slots in the bumpers for the '72 style jack either.
A footnote here is that the trunk lids are easily changed due to damage etc. so if it isn't original paint, (or documented) then who knows what has been done in it's past?
