Four barrel carburetor for slant 6 Offenhauser manifold?

I've got the same set-up as you have, but not installed yet. The carb I have is off a 1966 273 v8. Should work great. There is even a Mopar high performance manual for these slant 6's. That manual recommends using one of these carbs from a 1965 to 1967 273 v8 4bbl. It also gives recommendations for jet and rod changes.