One of the oddities of the A3D configuration is the change to, but apparently not a retrofit of, the fuselage fuel system vent.
It was originally a very small vent mast on the lower side of the left horizontal stabilizer.
Even after the bottom half of it was painted red, it's not very noticeable:
For some reason, on all A3Ds starting with Bureau Number 142650 and subsequent, both Bombers and Versions, the fuel vent was changed to a large mast extending from the left side of the aft fuselage. (The small red tube below the fuel vent mast was added at the same time; it was a drain for the vent system.)
The change coincides with the introduction of the tanker kit in production. It must not have been changed for a particularly important reason, since it doesn't seem to have been retrofitted to A3Ds before BuNo 142650, even on Skywarriors that have the tanker kit installed.
Training the Right Stuff, is now available from Amazon Books, HERE.
Scooter!, a history of the Douglas A4D Skyhawk, is available from Amazon Books, HERE. Strike from the Sea is the attack version of my earlier book,U.S. Naval Air Superiority. Like Air Superiority, it begins at the end of World War II. Whereas Air Superiority describes the Navy's transition from propeller-driven fighters to jets, Strike traces the development of U.S. Navy carrier-based attack aircraft, weapons, and mission capability. It also provides a segue to the current generation of strike fighters, albeit with a gap that is covered in my monograph on the Grumman F-111B. If you liked Air Superiority, you'll want to buy Strike as a companion volume.
In 1956, at age 12, I lived on NAS Sangley Point in the Philippine Islands. Always enamored with airplanes, I imprinted on the Cougars, Banshees, and Skyraiders then being deployed. Not able to be a Naval Aviator because I was nearsighted, I instead became an aeronautical engineer and general aviation pilot. Now retired, I write books and monographs on U.S. Navy aircraft.