In 1966, Chrysler introduces the sweptback Dodge Charger to run in NASCAR. This radical design was to make the car more aerodynamic. Instead of relying on brute force power to push the car down the track some manufacturers like Dodge, Ford, Mercury, and GM now realize they need to cope with air as a disaster problem.

In 1959, Chevy introduces their ‘Batwing’ car and it proves to be a disaster, both on the track and in normal driving. The car fishtailed and would sometimes raise the back end at a dangerous angle. In 1965 AMC introduces the Rambler Marlin’, the car had a fastback design and was aerodynamic. So, Dodge in 1966 copies the AMC design and introduces a 1966 Dodge Charger to run NASCAR. Now the speeds were pushing close to 180+ on the bigger tracks, the air was now an asset. Ford and GM jumped into the fastback craze. Ford introduces the Torino and the Mercury Cyclone. Chevy did not go that radical and introduces the Monte Carlo.

The 1966 Dodge was called the ‘Ugly Duckling by some critics but was proven a winner in 1966 the ‘Ugly Duckling’ Dodge won the NASCAR Grand National championship with David Pearson at the wheel. In recent years the 66 and 67 fastback Chargers have fallen out of favor with car collectors and enthusiasts.  But now has made a comeback. The 68 and 69 Chargers are one of the most sought-after cars on the market and in some cases unattainable at a reasonable price, that now the 66 and 67 Chargers have increased in popularity. (See Hemmings link) So the ugly duckling has made another comeback.

https://www.hemmings.com/blog/article/1966-67-dodge-charger-2/