Hmmmm- - - -that is an oddball fitting- - - -never seen one exactly like it! The small hole won't be a problem, as there is very little volume of flow to operate the vacuum advance. I'd be tempted to replace the fitting with one that has a 3/16" inverted flare female thread toward the distributor, and a 1/8" NPT male thread into the carburetor.
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
Love your enemies and drive 'em nuts!