Intriguing 1964 Mercury Comet A/FX Caliente factory drag class car with the 427 cu.in./425 hp V-8 — At least, that’s my best guess.
The FX stood for Factory Experimental, a class which allowed manufacturers to fit the largest engine available and alter the body of a production car. The letter A refers to the engine size; there were also B/FX and C/FX classes.