First, there are the obvious similarities: both are roadsters (though the XK120 was available as a drophead and fixed head coupe--the latter of which is also a "logical" extension of the F-Type); both are front-engine, rear-drive sports cars; both are wrapped in the quintessence of Jaguar style, each of their era; and both wear the Jaguar name.
The XK120 was Jaguar's first post-war original effort, born into an era of ongoing rationing, poor fuel supplies, and, both in the U.S. and the U.K., a burgeoning sports car culture.
To call the XK120 a success would be to understate the matter. Its first racing variant, the XK120C--later known as the C-Type--took two overall wins at Le Mans. The D-Type that followed it won three years straight from 1955-57. The Mille Miglia, Targa Florio, and Tourist Trophy races were all on the XK120's competition roster as well.
An XK120 FHC (fixed head coupe) was also the first non-American car to win a race in NASCAR. Al Keller piloted the XK to victory at Linden Airport in New Jersey on June 13, 1954. The race, called the International 100, was also the series' first road course event.
The XK120 road car itself set a number of records, including the record for highest average speed over 24 hours with Sir Stirling Moss at the wheel in 1950; the record for a one-hour run of 131.83 miles with Leslie Johnson at the wheel in 1951; and the record for a full week of high-speed driving, averaging 100.31 mph in 1952 in the hands of Moss, Johnson, Jack Fairman, and Bert Hadley. During the continuous week-long run, the XK120 also set world or class records for 72-hour, four-day, 10,000-kilometer, and 15,000-kilometer stints.
But how does this relate to the F-Type?
Apart from Jaguar's Whitman-esque linking of the two through time and place via a high-speed run at Jabbeke, Belgium (which you can see in the video above), the relationship of the XK120 to the F-Type is, due to separation in time and market, more spiritual than literal. Nevertheless, there are some mechanical, or at least statistical, similarities.
The XK120 was built largely of aluminum, including an all-alloy body--much like the F-Type. Dimensionally, the two are rather similar as well: the XK120's wheelbase is just 31 mm shorter than the F-Type's; the XK120's height is 26 mm taller than the F-Type's; the XK120's overall length is 76 mm shorter than the F-Type's; but the XK120 is 348 mm--13.7 inches--narrower than the F-Type.
Despite the XK120's relatively compact dimensions and lightweight construction--and without the safety, electronic, or other gear offered on the F-Type--it was only 600 pounds lighter than its modern-day descendant.
The F-Type also has yet to build its own racing portfolio, but if Jaguar's efforts with the modern XK are any indication, that's just a matter of time.
How else does the F-Type differ from the XK120? In almost every other manner possible. We'll be detailing the F-Type's technology and equipment in the weeks to come, so follow our 30 Days of the 2014 Jaguar F-Type series to learn all about the car--including our first-hand experience with it, to come later this month.