A dished head header assembly for a heat exchanger having a containment body that includes a rounded, or dished, wall portion forming an interior cavity. A flange attaches to the containment body and fastens the header assembly to the heat exchanger. A plurality of refrigerant passageways are extended through an opening in the containment body into the interior cavity. At least one baffle is attached to the rounded wall portion. The baffle divides the interior cavity into a plurality of sub-cavities. At least one divider divides the sub-cavities into a plurality of chambers. The plurality of passageways includes an inlet connection and an outlet connection for a plurality of refrigerant circuits. Each passageway is disposed in a corresponding chamber of the plurality of chambers. Extensions into the headers with diffusers insure efficient operation and performance of the heat exchanger. The adjustable flow restrictor plate maintains optimum velocities to further enhance performance.