So you're the original owner?
I don't think you're going to find out how many spoiler-delete cars came from the factory. It is my understanding that there are no official numbers from the factory. I know one guy who got a spoiler-delete and the window sticker doesn't show it. A number of guys did their own spoiler deletes later on, so people buying one from a private party won't necessarily know for sure if it came from the factory like that, especially if the window sticker doesn't show it.
Im the 3rd owner. I was lucky enough to get all the original documents when i purchased the car. It doesnt mention it on window sticker but does on purchase order.