Four barrel carburetor for slant 6 Offenhauser manifold?

Headers are on the list. I have not torn into the carburetor yet because I want to make (reasonably) sure it would work good. Perhaps that's why the secondary's are stuck closed as I mentioned earlier, I do not know much history on the car but has been sitting for over 25 years.
Well you can't be anything of "sure" of that if you don't rip into it