The out-of-production sheet seen here is one of two that I am aware of that is for the out-of-production 1/72 Heller EC-121 Warning Star kit that can be found on Ebay from time to time.  Those seeking alternatives to the limited offerings in the kit itself would be relieved to find this sheet, which I ordered online from djhobby.com.  They had a large number of discontinued sheets that took the opportunity to order.

The following history is taken from the website of the National Museum of Naval Aviation in Pensacola, perhaps the best museum of any type I have ever visited.  Its collection, presentations, and layout are superb. "The Lockheed EC-121 "Warning Star" is a variant of the C-121 transport aircraft. Utilized for airborne early warning, it employs a radome height-finding radar antenna (called the "camel back") on top of the fuselage and a large radome under the fuselage for a 20' search radar. It was powered by four Wright R-3350-34 turbo-compound engines. The fuselage was pressurized to accommodate electronic technicians and their associated mission equipment at high altitudes. Of the 142 C-121s ordered by the Navy, several in the transport version fulfilled the Navy's obligation to the Military Air Transport Service while the balance in flying Early Warning Barriers over the Atlantic and Pacific Oceans. A portion of this role ended in 1965, when an advanced radar system assumed the responsibility over the northern approaches to the North Atlantic - a mission previously assigned to Navy EC-121 squadrons for ten consecutive years. This "Jack of all Trades" aircraft was also employed as both a weather, electronic- and photo-reconnaissance aircraft. "

The first aircraft is reported as an EC-121K serving in WV-2/VT-86 at NAS Glynco, GA in 1976.  This particular aircraft was retired to the Naval Aviation Museum in 1973, so I guess their date was wrong.  Photos of this aircraft can be found on their website and at this link: http://personal.riverusers.com/~elmccaul/ac143221.htm

The second example is for a WC-121N weather reconnaissance aircraft of VW-4 out of Jacksonville NAS in 1958.  It was used as a hurricane hunter.  Overall, the aircraft is an unusual blue, FS15042.

The final example flew with an electronic warfare squadron that later flew EA-6As and EP-3s, VAQ-33.  The unit was assigned several aircraft types at once, including Skyraiders, F-4s, A-6s and EA-3 Skywarriors while they had the EC-121 for different types of EW training missions.  I have included a picture of this particular aircraft at the Boneyard in Arizona following its retirement.