Chances are they were a Ninth AF squadron...by the time of D-Day, I believe the last remaining 8th AF Thunderbolt Group was the 56th FG. As the Allies advanced inland, the 9th AF was deployed to the forward bases to provide primary ground support duties while the 8th was still dealing with air superiority (strategic bombing and air-to-air with the Luftwaffe). This does not rule out the 9th engaging in air-to-air of the 8th providing ground support missions. Chances are, though, the P-47s came from a 9th AF group.
I have to admit that I wasn't watching the aircraft close enough to pick up the letter codes on the fuselages.