Carburation Question

Even the 318 Carter BBD is too rich for a stock slant six. Unless you upgrade the exhaust and re-curve the distributor you'll probably not show much benefit from the swap. Even then, you'll need to lean that carburetor out some in the idle circuit. A Holley 350 is a better choice for tune ability, as more parts are made for them. If you plan to leave the engine stock, a Weber 2 barrel or a Super Six carburetor might be a good choice. The Super Six carburetors will cost you though.