Depending on the carburetor, there might be a vacuum port about halfway down the main carb body casting. Some 2G Rochesters did not have a ported vacuum fitting. The port you're looking for should have no vacuum at idle, and the vacuum should come on with a small amount of throttle opening as the engine speed is increased. The simplest way to find the right fitting is to use a vacuum gauge and look for a port that gets its vacuum at part throttle.
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!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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