sealing hood to Carb any HP gain?

You could do like the A12 Roadrunner and Superbee style air cleaner or AAR and T/A Style with a rubber between the base plate and hood. You just have to make the base plate larger than the opening on the hood.
You could also fabricate a cover atached to the hood with a hole just big enough for the air cleaner to poke through.
Hope this helps.
Emilio