A4D-1: OCT 1952, no refueling probe, no radar, three hard points. Re-designated the A-4A in OCT 1962.
A4D-2: MAR 1956, refueling probe, no radar, three hardpoints. Re-designated the A-4B in OCT 1962.
A4D-3: 1957, none built. Douglas proposal for a improved A4D-2. U.S. Navy never funded, project...