Shelby Quarter Horse
In the late ’60s, Ford had several successful performance editions of the Mustang, but even so, Shelby developed a few of his prototypes to explore the platform’s limits further. Known as the Quarter Horse, pre-production prototypes built in 1969 have featured many exciting design cues linked to Shelby and Boss Mustangs (via Motor Trend).
Those cars had a Shelby front end with a Mustang rear end, a Boss 429 engine, and a Mercury Cougar dashboard. The idea was to produce a cheaper Shelby GT 500 but Ford killed the project in 1970.