Yes, it's necessary, but you can probably adapt one from a Quadrajet or some other carburetor if you're willing to make a mounting bracket. It's supposed to catch the throttle linkage just before it closes all the way, and ease it down to the idle position. The dashpot doesn't know what carb it's on, so just find one you can adapt.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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