B-D, I dont know a whole lot about spoilers but I have noticed most of the S10's at the track, at least around here, use an aluminum bed cover that extends about 12 inches past the tailgate. There is a plate welded on each side from the rear corners of the cover down to the bottom of the tail lights. You may not be getting a mental image of what I'm talking about so I'll look around on the net and see if I can find a pic of one of these. I dont know if it works or not but I have seen at least 4 different trucks with this same design. I hope this helps.
Here is a page that shows a few images like I was talking about....when you get there click on pro stock truck and it will give you a list of names...most of them are running S10's. Craig Eaton has the best looking in my opinion.