intake gasket ?

I'm betting Ma Mopar put that chamber around the crossover passage in there just to save weight. Less iron = less weight = less cost.

Daily driver with old pump gas, and very low outdoor temperatures, you needed the crossover. With today's gas you probably don't want it. Remove the flapper in the RH exhaust manifold, and block off the intake manifold passages on cars that are driven in nice weather only, have an electric choke, or EFI.