In looking up information to respond to a request, I was reminded of this unique Grumman. It was the cargo version of the venerable S2F ASW airplane, modified to be the aerodynamic prototype for the AEW version of the airplane. The addition of the big radome over the fuselage required the change shown here to the empennage and also a change to the wing fold arrangement. It did not have the stretched fuselage of the production airplane, however, as evidenced by the red propeller warning stripe being so close to the aft edge of the pilot's side window. After flight test, the dummy radome was removed and the airplane resumed its role as a transport.
The production airplane was originally the WF-2, redesignated in 1962 as the E-1B. Strictly speaking, there was a WF-1 but not an E-1A, since the WF-1 was cancelled at the mockup stage. It was to be an S2F airframe simply modified with an APS-20A mounted above the cockpit. This would have preserved the original empennage and wing fold arrangement, albeit with the addition of small fins on the horizontal stabilizer to maintain directional stability.