The 1400 is the "emissions" carburetor and it has a ported and EGR vacuum port on the front (no manifold), though I'm thinking the power brake port on the back could be used for manifold vacuum. It also has a specific fuel vapor connection for the charcoal canister (if you have one). The manuals don't have any tuning changes for the 1400 since Edelbrock looks at it as a carb that shouldn't be altered. I'm not sure if anything else internal is different between the 1400, 1405 and 1406.
