Recommended 4bbl carb for stock 318

The 1406 Edelbrock is perfect. It's a 600 CFM carburetor, yes, but it is lean because it is tuned for economy. The 1405 is the performance version and would be a little fat. I would use the 1406 all day long, because it leaves some wiggle room if you add upgrades later on. It will work fine.