intake fittings

[76bonanza]

I have found a vaccum fitting for my intake with the ports I need but have a few questions. First is the vaccum hole 3/8?(edlebrock air gap dont think it matters tho)

Second looks like the PO used some kind of goop silicon or something when I remove the old fitting and clean the hole what should I use to seal it (I was thinking plumbers tape or something.) And about how tight all the way in till very snug or just so long as it is in a fair bit?

Thanks for your help I know this may seem easy just never done it before.