As Mr. "Sixteen Grand Sedan #56" and I discussed elsewhere today, I used the same auction and those pictures in my discussions with some other racing folks I've communicated with about a potential match for the thread starting TRACO stickered valve covers above. Additionally, I turned one of those racing friends on to these items
, found because of the same part number reference.
However, I've yet to mention part numbers on this forum, because it's not completely clear which number references a cover with and without tabs. Additionally, there are several references to this part number, including the GM parts book references, that would lead one to a cover with different features.
Mr. "Sixteen Grand Sedan #56" looked into this more in depth today, and perhaps he's found something a bit more conclusive. And the folks with original '67 GMC trucks with these covers, without tabs (probably the passenger side cover), may also be of help soon. I will continue with the effort, and hope to provide something a bit more concrete.