Regular production Mercury Cyclones had a then-fashionable inset grille and headlights, which fared poorly in the wind tunnel.

The Mercury Cyclone Spoiler II had this nose replaced with one that extended the car's length by about six inches, with a flush-mounted grille identical to that used on the Ford Torino Talladega giving it a much more aerodynamic front end.

In a well kept, secret design move,[citation needed] the rocker panels were reshaped and rolled to allow Mercury teams to run their racing cars about an inch closer to the ground while staying within NASCAR rules; this also greatly enhanced the top speed of the car by lowering its center of gravity, and further reducing its wind resistance.

All production (homologation) models of the Mercury Cyclone Spoiler II were equipped with a 351 Windsor engine, automatic on the column, and front bench seat.

Later in the season, the Boss 429 engine was used by many of the teams, after it had finally been declared "officially homologated" by NASCAR president, Bill France.