There is only one.
Ford made only one 68 XL fastback with bucket seats, AC, 390 and C6 - and it sold in 2020 for only $2,500 (now it's been restored)

In 2020, in the small town of McMinnville, Tennessee, this 1968 Ford XL sold for $2,500.
The Ford had no visible rust, and it appeared to have all its original drivetrain intact, and the buyer, Jay Atwill, was able to drive it home and made the 70-plus-mile trip without any issues.
The car was original, including the 390-cu.in., four-barrel equipped big-block engine and C6 automatic transmission, and the only piece of original documentation he found was the original title, when Clayton Barritt bought the car new in Phoenix, Arizona.
One of 50,045 XL Fastbacks, one of only 52 with this engine and transmission configuration that was factory-painted Light Beige. One of 10 with bucket seats, one of six with a black vinyl roof, one of two with Ford’s single key system, and one of one with air conditioning.

 

 

 

 

 

 

https://www.hemmings.com/stories/1968-ford-xl-fastback-restoration/