The F-4E variant was an improved version of the C/D with an elongated nose and compact radar. These two things made it possible to install a 20mm M61A1 6 barrel 640 round Vulcan gun pod in the nose. The F-4E was the most produced variant with 1387 aircraft being made over its 12 year production period. The “E” also equipped more air forces than any other variant of the Phantom II.
USAF 65-0713 c/n 1761 is noted for a few reasons; it was produced as an F-4D, modified as the prototype for the F-4E armed with an M-61 rotary cannon. It was decided missiles were adequate and cannons weren’t added to production models. Brigadier General Charles “Chuck” Yeager took his last flight as an active duty USAF pilot in this aircraft. 65-0713 also was the test aircraft for the F-4G Wild Weasel and as well as other test beds throughout the 1970s and 80s. This aircraft is on display at AFFTC Museum, Edwards Air Force Base.

Info: McDonnell Douglas YF-4E Phantom II - AFTC, USAF, 1985