I seem to remember that the Holly I put on my 69 Cougar had one you screwed in or bolted in there. Those carbs are generic so they have to be adaptable.
As for your vacuum.
Fortunately you've made your life easier by going off the smog grid. I'm assuming you don't have to smog that tin can in NV, eh?
We talked about it before, but here's what I would try.
Ported vacuum to your distributor
manifold vacuum to your brake booster and your
tranny.
Manifold vacuum to your vacuum reservoir (you have AC, right) and the line from that can goes to your heater valve.
Pretty simple.
I think.