The car shared its 10-foot (3.05 m) wheelbase with its predecessor, the Jaguar Mark VII M, which outwardly it closely resembled.

Distinguishing visually between the models is facilitated by changes to the front grille and a curved chrome trim strip below the waistline which allowed the factory to offer a variety of two-tone paint schemes.

Although introduced subsequent to the 'C' type competition head (as used on the C-Type racer and available as an option on the XK 140) this naming made more sense than might at first appear.

The modified head supported by twin SU carburetors, and employing a manual four-speed transmission, meant that advertised engine output was now increased to 190 bhp (141.7 kW): the claimed top speed in excess of 106 mph (170 km/h) was considered impressive, given the car's bulk.

A Mark VIII, crewed by Dunning and Cash, won first place in the Automatic Transmission class in the 1958 Australian Mobilgas Economy Run, which was a fuel economy contest in which cars were required to cover 1,224 miles in two and a half days.