That is in Dearborn, the brick wall in the background is the "wavy wall" that surrounds the Dearborn proving Grounds and separates the Henry Ford/Greenfield Village from the grounds.
The brick wall appears to be the "wavy" wall around the Dearborn Engineering test track, and this looks to be a Road chassis, so likely P1028, however didn't P1013 also use "GT 40 PR" in Europe?
Jim is correct, it's GT40P/1028. The GT 40 PR plate was used on 1028 and 1013 but wasn't a genuine registration number in either case, 1013 going on to be registered as OVX 355D.
Damn it. Google keeps changing the link so that it only appears in the same place for a few hours. The hell with it, I downloaded it to my hard drive and will now upload it here so it will be here now and forevermore! :veryangry: