It stands for 40 inches, as in the height of the car.
I, too, would really love to see a Ford GT racing. Some would say it's for monetary reasons, but I doubt Spyker has nearly as much money as Ford does, even with Ford falling on hard times. One question: is this Spyker factory backed, or being run by a private team? I know it has a Dutch flag on it and it's in the normal Dutch orange livery, but it could be run by a private Dutch team that bought a couple C8's and transformed them.