Okay...
I found two possible brackets at Summit:
http://www.summitracing.com/parts/hly-20-58/overview/
http://www.summitracing.com/parts/hly-20-72/overview/

...and a dashpot:
http://www.summitracing.com/parts/hly-11-4

From the description for the dashpot:
"These Holley carburetor dashpots are designed to be used on manual transmission vehicles. They will prevent engine stalling on sudden deceleration, fits most Holley dashpot brackets."

I can't see how the bracket(s) would fit, and can't find an installation guide to clarify. How would I know which bracket to get, and why does it say the dashpot is to be used on manual transmission vehicles?