I went digging for further clarification on the dealer-installed options. I was able to get in touch with Alan Bigelow, the fourth generation operator of Bigelow Chevrolet where this car was bought new. He was a young man working at the dealership under his father in 1973. He went back and talked to his dad and one of the mechanics from that era that is still very close with the family. He confirmed with them that the carburetor, intake and ignition were items that the dealership would install there prior to the sale, and then send the new car owner to a local muffler shop to have headers installed after the formal sale was complete. That way the smog unit wasn’t removed by the dealership. It allowed them to stay compliant with the Clean Air Act and their franchise agreement with General Motors. He is sending me an affidavit stating this to keep with the rest of the documents that I have regarding the history of this vehicle. On a sad side note, Bigelow Chevrolet was one of the GM dealerships that was closed in 2010 when GM downsized. It is sad to see a family that opened their dealership in 1911 and endured 99 years of the ups and downs of the car business lose their franchise after all of that time. I can’t imagine having a family business yanked out from under you after all of those years!