A connector sub-assembly includes a dielectric carrier, plural signal conductors, and a ground frame. The dielectric carrier is defined by first and second overmolded bodies that engage one another at an overmold interface. An intermediate segment of each signal conductor is encased within the dielectric carrier. The ground frame is held between the first and second overmolded bodies at the overmold interface. The ground frame includes a ground bus bar encased within the dielectric carrier and plural ground conductors extending from the ground bus bar. The second overmolded body is formed in-situ on an inner side of the first overmolded body. An inner side of the second overmolded body at the overmold interface is partially defined by a profile of the inner side of the first overmolded body and partially defined by the ground frame.