What type of vacuum fitting for a 67?? 2V carb?

I rebuilt a carb I was told came off of a 67 Mustang. The ID number on the base of the carb reads 7D<space>R. It was nice out today so I was going to swap it with the original on my car and then rebuild mine. While taking mine off I noticed that the vacuum line from the carb to the VAD screws into the base of the carb. Looking at the rebuilt carb I notice that the same area is essentially flat and there's no threading inside the hole. The question is what type of fitting do I need to get for the rebuilt carb? It doesn't seem right to me unless there's a rubber plug or something that goes in there. I can't imagine the vacuum not leaking if all you're supposed to do is put a tube in there without securing it.

Heres a pic in case you feel like taking a look

Thanks

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