How about totally removing the air box.
Personally (and I know most people don't agree with it) I prefer the airbox system. I think that it makes filter work a lot easier and reduces some of the turbulence in the incoming air stream. If the airbox was removed and the system still pulled air from outside the car, that is fine. I think one of the things that most people miss when they upgrade to a tube with a filter on the end, is that they air now pulling air from behind the radiator. Heat = less HP. There isn't a lot of HP to be gained in a normally aspirated system anyway (not saying there isn't any) but you can easily wipe out your gains from reducing restriction by pulling warmer air.
While I don't know if it would be possible, a dual airbox similar to the M5 would definitely be something I'd be interested in over removing the airbox.
My reasons are simple. I know what the numbers are, and unlike the f bodies I'm willing to bet that the induction on the GTO is much less restrictive. Sticking a tube and a filter to pull warm air is silly to me (Yes, it works better on the track where hot oil + cold air + cold coolant = more power. If the radiator is cool there isn't an affect on this type of replacement) since this is a daily driver to me and that type of induction is pulling from a hotter spot (likely) then the existing box.
Of course, I want to qualify *ALL* of this by saying, I don't have my GTO in my hands and haven't seen the exact routing of the factory airbox and associated goodies. I was told the car has a ram air system by pontiac which I assume means its pulling air from outside the car, through a tube, to the airbox and then to the intake.
When I get my car, I'm sure I (and everyone else here) can give a better idea of exactly what they are looking for.
I will say though that whatever product you have won't be purchased by me if I need to cut body panels in any way shape or form. If I can't return the car to stock appearance with a ratchet set and a set of screwdrivers, its not in my future.