Re: edelbrock 1406 carb.
The engine won't care which port you connect to but if you have problems idling then the manifold vacuum port will help the idle more than the ported vacuum. Manifold vacuum drops when you start to accelerate so it will retard as soon as you begin to accelerate so above idle it will make no difference.
66 Mustang Coupe. 365hp, 4spd Toploader, sub-frame connectors
Shelby drop, suspension tuned for slalom and hill climb
body mods and weight reduced to 2000lbs; name: Muskrat