[3macs1]

First I would like to say your collection is wonderful. On the carb spacer I am not sure if they were ever factory installed but we definately bought them over the counter from GM when I raced my 70 Chevelle years ago. There was one for holley and one for quad.They helped with controlling vapor lock and fuel boiling in the bowl especially on the holley with the GM Al intake by preventing all of the heat from getting to the carb especially after shutting the engine off. Some believed this cooler carb would produce a denser fuel mixture and make more H.P. We also used a Gm deflector pan under the GM Al intakes which again I bought over the counter to keep the oil off the bottom of the al intake and the heat down. I am not sure if GM still makes these items perhaps someone more experienced than me can let us know.I still have one of each NOS buried somewhere if part numbers are required.
Joe