I notice tops of the ribs are also painted black. Other posts seem to have concluded they were bare or painted silver.
They were originally. Not unusual for unrestored cars to have owners that took the black rattle can to freshen up sun burn/worn surfaces on the shaker and engine compartment. Pictures I choose to post were not focusing on the finish - just the emblem or lack there of
Neither of the bottom two have the drain hose and other details like new or prefect. Plus there would be other differences depending on where they were originally delivered or built for
Hard to tell if the top one, only one that does not look repainted for sure, but bad angle for the detail