Another picture of it is here:
http://www.geocities.com/jamsvx2/modifications.html
(The picture next to the section on rear spoilers)
OK, take a look at the second car in from the front in this picture. Its the same rear spoiler, is that one of the prototypes as well? This is from Jamsvx's site, maybe he can tell us where it came from.
You may have to download it and zoom in on that section with image editing software in order to really see it, but it looks at the very least extremely close to the other one I asked about.
And on the subject of Ford prototypes, yes, they do keep them. They actually auctioned a large number of them off a year or two ago, but most of them couldn't be driven for reasons other than a lack of VINs (ie no engines, etc).