[camarojoe]

The covers are NOT made by Chevrolet, they were always an aftermarket cover...the Chevrolet name cast into the back just means that the particular casting FITS Chevrolet... similar covers were also made for ford, mopar, etc. The 3 bumps you refer to are actually the bosses to attach screws when installing the baffle plates under the oil fill/breather. These are now being re-cast today, which is why you see so many sets on ebay with various emblems (Yenko 427, ZL1, Nickey, etc. etc.) stuck in the holes... These were sold under various brand names over the years, but were never made by or sold by Chevrolet.