The 1969 Mark III was created when Lee Iacocca, president of Ford Motor Company at the time, directed Design Vice President, Gene Bordinat, to "put a Rolls Royce grille on a Thunderbird" in September 1965. The Mark III was based on the fourth generation Lincoln Continental (1961-1969) and the four-door fifth generation Thunderbird introduced for 1967. With the Thunderbird "dying in the marketplace" Iacocca wanted to put the company's development investment to better use by expanding its platform over several models.

The Mark III was intended to compete head-to-head with the top of the domestic personal luxury car market, Cadillac's heavily redesigned front wheel drive Eldorado. This placed it above the second tier premium personal luxury cars such as the Ford Thunderbird, Buick Riviera and Oldsmobile Toronado. As the Eldorado was built upon the Toronado frame, the Mark III's was based off the Thunderbird's. While the side-rail frame was identical to the Thunderbird's, the Mark III bore almost 300 lb (140 kg) more bodywork. Power was adequate from Lincoln's Ford 385 engine-based 460 cu in (7.5 l) 365 bhp (272 kW) V8.

Introduced in April 1968 as an early 1969 model, the model was a remarkable commercial success because it combined the high unit revenue of a luxury model with the low development costs and fixed cost–amortizing utility of platform-sharing, in a car that was appealing enough to buyers that many units were sold. Iacocca said, "We brought out the Mark III in April 1968, and in its very first year it outsold the Cadillac Eldorado, which had been our long-range goal. 

Source: Wikipedia

Photography of the car interior with kind permission from Sav & John at noyzboyz, Scarborough (Toronto).