The wagon was named "Mrs B's Grocery Getter".
Pontiac made a total of 14 Tempest 421sd cars. Fourteen. Then again these were A/FX cars, not S/S cars, so like the 427 Falcon/Comet cars there were a lot fewer of them.
Probably fore-runners of the famous Royal GTO that beat Ferrari in the 1964 CD article, the one that was a 389 GTO but really a 421 GTO as admitted later. Milt Schornack said in his excellent book that he did not really like that idea. I didn't like it AT ALL, as it was basically lying to the customer to run that car around Detroit streets pretending it was the same 389 you could buy from the factory. And it ran 105mph in the quarter, not 115mph, you can see from the whole article that the 115mph is a misprint - that was its top speed!