I would say it is a hybrid of a Greenlight "red test shot" and a pre-production piece.
Here is a Greenlight red test shot Mustang I have .....
As you can see, the "hardtop" portion is plastic and it is unpainted. This is how you normally see GL "red test shots".
The top on yours is painted, so it might have been an existing part put on to see how it would look. It's hard to say. All the other features, red body, black plastic engine and side pipes, and bare metal base, would point toward it being a "red test shot". I did notice that the car is missing the interior which is a bit odd. I guess it just adds to the mystery.
Its a pre production piece. There were 4 sent. 2-Roadsters and 2-coupes. The 2 coupes came to display the different hoods 1-being the L88 hood the other the stock hood and the 2 roasters where to display 1 with the top up and the other with the top down and a hood option. The lack of the interior was what was so significant. I suppose that because the roaster with the top down had a clear view to approve the interior, that they didn't need to put it in the top up version. Or it could have been that it could have been a error. Because Matt sent them to me to just to approve, as long as I could see the interior in one, it worked so we never discussed the lack of interior. I enjoyed doing the pre-production work on the Corvettes because being a Mopar specialist, I never really put efforts into learning anything about Corvettes specifically, until I did this job bag. It was fascinating learning specifics about the Corvettes though out the years. Until this date, despite all of the Mopars I owned and drove the Quickest street car I have ever been in, was a 67 Corvette powered by a L88 with 513 rear end gears. Thanks for playing