I ran into this by accident but apparently there was a topless GT40 racing at the 1965 Le Mans. So the GTX1 isn't such a new idea but now it has a good lineage to the past. This is a 1/24 scale model but there's historic pictures out there.
Last I heard, Dean Jeffries in socal still has one of those sitting in the back of his shop. He has had the car for decades. There were only several of those built.