The Jaguar S-type 3.4 and 3.8

The S-type was marketed as a more "executive" car than the MKII, and although the interior appointments were similar there were a number of detail differences. The seats were different (and lacked the picnic tables which were a feature of the MKII),  and the dash center section (click for comparison) was covered in walnut instead of the black leather of the MKII.  The different roofline and seats gave more rear seat leg and headroom, and the independent rear suspension gave a much smoother ride than the live axle of the MK II models. All this was at the expense of extra weight, and softened performance however, when compared to the like engined Mk II's.

It is thought that originally the S-type was to have been the MK II's replacement - the MK III, but several reasons are put forward by historians to explain the fact that it was given a different name, and marketed alongside the MK II, and did not replace it. These are firstly that the MK II was still selling well, and secondly that the S-type was seen more as an alternative to the slow selling MK X in territories where this was not selling well. This is also borne out by the way the S-type itself evolved into the 420, although again all models remained on sale and were eventually phased out at about the same time.   The overlap between models in the 1960s was considerable, and some territories such as the USA did not import all models in order to avoid confusion. For example in the early 60's the models on sale in America were the MK II 3.8, the MK X, and of course the XKE.   When the S-Type was introduced, only the 3.8 model was imported into the States, and the MK II 3.4 was substituted for the 3.8 model. .