The interior is the last Jaguar with the traditional wood work. Upon the introduction of the XJ, Jaguar limited wood work to an inset plank on the plastic molded dash, later adding filets to the doors and sometimes small picnic tables to the backs of the front seats. In the Mark X however, the dash is entirely made of wood. The wood work not only appears at the base of the windows, but also goes completely around them. Both over the front and rear windshield, and the sidewindows have woodwork above them. Large bookmatched picnic tables fold out from the front seats. Some vehicles have an additional pull-out picnic table up front, as well as wood escutcheons for the heater controls and electric window switches.
The suspension was independent all round with coil springs at the front. Two engine sizes were offered with 3,781 cc until 1964 when the larger 4,235 cc unit took over. Manual, manual with overdrive and automatic transmissions were options but most cars left the factory with an automatic. In 1966 the Mark X was renamed the Jaguar 420G. It was discontinued in 1970 as XJ6 production increased.