Ford capitalized on the extremely popular design of the Mustang by leaving it alone. For the most part, changes in 1966 were limited to minor revisions.

The 1966 Mustang’s sheet metal was identical to that of the 1965 model. The black honeycomb grille was replaced with bright horizontal bars and while the running horse emblem in the center of the grille remained, the four bars extending from it were deleted. The simulated air scoop in front of the rear wheels was updated to a three-prong design.

A five-gauge instrument cluster with a speedometer reaching 140 MPH was introduced on all Mustangs. The warning lamps of the previous version were replaced with an oil pressure gauge and an ammeter. Other changes to the dash included a redesigned glove box door and reshaped dash crash pad. Standard upholstery also received minor revisions. The vertical door panel pleats of 1965 became horizontal in 1966 and seat inserts were knit-weave vinyl, replacing the smooth inserts of 1965. The deluxe, or “pony” interior did not change for 1966, however this would be that last year this popular design would be offered.

Two engine options, the 170ci six-cylinder and the 260ci eight-cylinder, were dropped in 1966. The three-speed manual transmission was standard (except for the HiPo), with the four-speed manual and C-4 Cruise-O-Matic available as options for all engines.