Interesting was the 1966 Banshee Show Car code named XP-798. This was JZD’s concept of a "Mustang Fighter" with all wheel independent suspension, a 421 V8, and fold down rear seats. Of note were the doors; flip-up panels on the roof augmented the passenger doors.
The Banshee was never shown to the public: GM President Cole thought it would eat into the Corvette’s market share and Chevrolet was developing the F Car which became the Camaro/Firebird. One could guess that the doors of the
Banshee made their way into the design parameters of the DMC-12 in 1975, but there was no mention of this.
Note that in 1988 the Banshee name was revived by Pontiac into a Show Car to demonstrate a Firebird for the 90’s, so any references may get confused here since the 1966 Show Car was never really, well, Shown.
Source: Eric Friedebach