The designation "FC-47" is interesting - a cargo aircraft converted into a fighter! (must've been back when the Air Force still had that 'we only have fighters' mentality).
That's ever only been done one other time, IIRC, with the FC-34 - which was redesignated ABL-1.
Some classified Gooney Birds:
P version nickname is "Banjo" when equipped with the QRC-346 jamming system and this long-wire antennas atop.
Q version targeted air defense systems.