Hello Jon,
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.
-Chad