I am tinkering with the idea of using the Autolite 1100 carburetor from a 65 Mustang 6 cylinder. It works with the loadamatic distributor and is a one barrel like the Holley 847. But as Cmbrucew stated, you need a carburetor that can work with the loadamatic distributor. Otherwise, I believe this is what you are looking for:
https://www.amazon.com/Trans-Dapt-20.../dp/B000N8GTL8
I am just not sure how well a two barrel will work squeezing down to one barrel. I have seen these with 3 bolts also.