Back on topic...
For those that haven't seen it, here's the video text (translated from French) from the FB post Wedgeman found:
"Carroll Shelby - Behind the scenes of the feat The period allowing me to explore the hidden corners of my hard disks, I propose tonight an interview with Carroll Shelby, aired on June 16, 1966, Thursday before the 24 pm, as part of the show "Behind the scenes of the feat". Well, starting in, it starts wrong with two spelling errors in Texas's name, but the rest is much nicer. We start with views of the Shelby plant parking lot at LAX where the Mustang GT350, that look black, so maybe of in finish. Then Carroll Shelby arrives in Cobra 289 and invites us into his office to tell us about his career. Next are images of the Mustang GT350, assembly line and the competition service, probably just after the 24 hours of Daytona 1966, as we see the winning MK II at the hands Ken Miles and Lloyd Ruby, P/1015, on a set and that other cars seem to be dismantling. The spider X-1 is also seen in the process of being assembled and the 7 litres test and break-in benches. Then follow pictures of a Shelby advertising film shot in Riverside where you see a GT40 (GT/105?), a GT350 with it, looks like Bob Bondurant at his wheel, and Ken Miles, filmed in the counter diving, literally having fun at the wheel of a Cobra. Beautiful images of the 24 Hours of Daytona 1966 take over and the report is already talking about the brake problems of the MkII. With respect to the images of the 12 Hours of Sebring, and because the report was probably closed in front, it dates back to the 1965 edition, the victory of the Chaparral 2 A of Jim Hall and Superbowl Sharp, and we present the footage of the second GT40, Ken Miles and Bruce McLaren on GT / 103 as the winners. After a very diplomatic speech by Caroll Shelby about Ford's chances of winning at Le Mans 1966, very rare images of the April 1966 Trials are presented. Carroll Shelby is dressed in black, probably to pay tribute to Walt Hansgen who killed himself the day before at the wheel of P/1011, crushing at the end of the Dunlop escape. Graham Hill and Jackie Stewart, present on behalf of Alan Mann, Ken Miles driving P/1012 and very rare footage and sound recording of J-1. Otherwise, take care of yourself and your loved ones in this difficult time."
If the comment regarding the GT350 production line is accurate and just after the 66 Daytona, I believe that would put it in very late Feb or early March 1966.