Dave, it sounds like you have a Carter WCFB which was available until 1965 from what I've read. They can be delicate and tough to work on, and some people just don't like them. It's an evenbore, and I think uses the same manifold Big Dave mentioned for the Rochester 4G.
Anyhow, welcome and enjoy your new ride!
66 Impala (in progress)
56 stepside shortbed
55 Bel Air sedan
02 Monte Carlo (bought new)