Question about very first Cobra

[strada5300]

This might have been discussed long ago on the forum but I wonder
   what the story is on the first Cobra, which here is CSX2000, though in early stories in 1962 it was mentioned as CSX1001. My question is, as I understand it, Shelby went to England to test the first prototype with a 221 cu. in. V8 at Silverstone and that, after the tests, that engine was taken out and the car shipped to America to become CSX2000. My question is, does anyone with history of Zephry-engined Aces know if one Zephyr-engined Ace was sacrificed to make CSX2000 or was  an all new chassis and body built for Shelby and not numbered until it was used for Shelby's mule? I thought maybe they kept the original chassis and body in England and just built Shelby another chassis to send to America. If my theory is right there should be one less 2.6 liter Ace accounted for today than the original production records account for. Also at some point Shelby made the trunk (boot to Brits) less deep to make the body more rigid and I wonder if that was done to CSX2000 or to later small block Cobras only.