In December 1976, the Navy approved the use of the EF-4B designation for F-4Bs that were serving with VAQ-33 in support of the Navy's electronic warfare support effort. Long after most F-4Bs had been retired to storage, five F-4Bs remained serving with VAQ-33 as high-speed targets and as threat simulators to train radar operators. They were provided with electronics countermeasures pods and jammers carried underneath their wings. By the time the designation change was approved, the only F-4B remaining with VAQ-33 was BuNo 153070. The last EF-4B aircraft was finally retired in 1981.
Two F-4Bs were modified as research and development aircraft under the designation NF-4B. They served in test work at the Naval Air Development Center at Warminster, Pennsylvania. The "N" prefix meant that structural modifications prevented their return to full operational status.