exhaust manifold hole opening

hi everybody , i just purchased a 65 barracuda with a slant 6 , have a exhaust leak from the top of the manifold brought it to a muffler shop ,mechanic found the leak which is coming from a circular small hole at top a little behind and below the fuel filter area , he was not sure what goes there and did not want to just plug it I can probaly send a photo of the area, any suggestions . its a raised short extension maybe comes up about a 1/4 " off the top of the manifold can see the opening between the intake manifold THANKS !