The threaded hole in the throttle base for the vacuum line is a 1/8" pipe thread, with a tiny hole drilled behind it. That's why we're recommending plugging and re-drilling. Swapping carburetor bases is a rookie mistake that people who don't understand how carburetors are manufactured attempt, rarely with any degree of success.
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!