Was that a custom bodied Falcon ?
According to the Falcon Challengers story written by Max Muhleman in the July 1962 Motor Trend, Challenger I was built by Holman Moody for the Sebring 12 Hour Grand Prix of Endurance. It was built in 10 days based on a Falcon Futura body. They finished 2nd in class behind a Jim Hall Chevy powered Chapparal.
The car was powered by a 221 cubic inch Windsor, bored out to 243.9 cubic inches, just under the 244 cubic inch limit. Compression was bumped from 8.5 to 10.5:1 and a 4V carb was installed. During the race the cylinder heads were replaced due to an oiling problem. Top speed was 135 mph and drum brakes were 3-inch wide in the front and 2.5-inch in the back.
A Challenger II had 3 inches sectioned out of the body center line.
A Challenger III, in the photo, was built with the 3-inch section along with the fastback configuration. The rear window was plexiglass with an aluminum roof.