carb vac fitting question on a '69

I just purchased a correct carb for my '69 with a 350/300hp auto. The carb that was on there was for a '69 350 4 spd. The only difference I can find is there is a vac fitting on the auto one right by where the fuel inlet is, what is supposed to go to this? (The 4 spd one does not have this fitting)
Thanks,
Matt

I dont know off hand what the different vac fitting is for..

the only thing i can think of that needs vacuum on auto and isnt on manual is the vac modulator.. but that runs off intake vac.

but in addition to the outside appearance. the vacuum secondary might have a weaker resistance spring.. allowing the secondaries to open easier and stay open during a shift.

btw what is the number and date on the old carb... if it is correct for 69 manual.. are you interested in selling it??

|UPDATED|6/20/2004 11:59:20 PM (AZT)|/UPDATED|

That vacuum line often went to the primary choke pulloff or the air cleaner for heated air intake. Some factory cars had it plugged, and didn't use the extra port.

Thanks Guys!

Matt