Carb Help!

[Merc09]

So i have a holley 600 single pumper. I bolted it down to my intake. I then noticed where there is a vaccum port on the front of the carb i can feel underneath it and feel the groove in the bottom of the carb. I think i need on of them carb spacers but i dont know how to find out which one i need and so on. If someone could help that would be awesome. Thanks! 

[johnjon]

squarebore to spreadbore 4bbl carb adapter.
a universal style with 2 bolt patterns can be found in the high performance section at advance auto/autozone.

[Merc09]

squarebore to spreadbore 4bbl carb adapter.
a universal style with 2 bolt patterns can be found in the high performance section at advance auto/autozone.

Thank you!