1967 was a transition year for Jaguar. In the area of saloons they produced the Mark 2, the S-Type, the 420, the 240, the 340, the 420G and the Daimler 250 V-8. Needless to say that whilst each of these saloons had it's own unique features, Jaguar had a LOT of duplication. 1968 saw the demise of most of these saloons in favor of the XJ6 and because of the newly passed safety regulations in the US.
Five of the above listed saloons were direct replicas of the original Mark 1 and Mark 2 saloon. The Mark 2 was still considered the flagship. The 240 and the 340 were less expensive models with vinyl interiors and less wood as well as the thinner S-Type bumpers and 2.4 and 3.4 liter engines. The S-Type was actually an upscale from the Mark 2 with "eye-lids" in the front and the extended trunk. There was more wood in the driver's compartment including a slide out tray. The S-Type also had the XKE Independent rear suspension unlike the solid rear axle of the Mark 2. The S-Type eventually took over as the police vehicle of choice due to it's "superior" handling characteristics. The Daimler was nearly identical to the Mark 2 with the exception of some creature upgrades as well as the first V-8 engine.
The 420 was basically the field experiment for the XJ6. It had the same front suspension as well as the same rear suspension as the new XJ6. The XJ6 had rack and pinon steering however. The 420 had exactly the same engine set-up as the first of the XJ6s. The 420 was also negative earth.
Finally there was the 420G. It was a monster compared tot he other saloons. It was a full 14" longer than the 420 and 10" wider. It had many of the refinements that were to become future standardsfor Jaguar such as power windows and air conditioning.