A couple things I see that could help fuel economy by improving your aerodynamics would be:
1. An bellypan for under your engine. I have heard numbers between 3 and 5% better FE, and I have heard better downforce, better cooling, and less drag. I can't say for sure how well they work, but if nothing else, an aluminum bellypan would help protect your engine and keep things a bit cleaner.
2. I don't know how vital your huge "mouth" opening is, but I would guess that in cooler weather and normal driving you could block most of it off. Your car will warm up faster and keep the engine bay warmer during winter type driving. You might even be able to fit something more "beak like" there that will force air OVER the vehicle.
You can find out more about these and other modifications by looking at the "
60+ Vehice Modications" at the top of the page (or using the link here).