I picked up one of the Challenger fiberglass spoilers from Jon that Brad and Mitch are talking about. I got one w/ the ducting cutouts. It's a nice piece - gray gelcoat and what looks like chopped strand mat. Like all fiberglass parts, it will need to be fitted. It is from a mold so there is a chance that there will be defects in the gelcoat that will need to be addressed if you are concerned about the spoiler looking cosmetically perfect.
This is what Jon said when I asked him about the installation:
Hey Jerry - The Challenger spoiler is the easier of the two to line up and install. The spoiler fits into place with the parking lamp bulge.
The top of the spoiler should be right below the lower air intake opening on the valance. An extra set of hands helps.
Most people have used nuts and bolts while others have used quick turn fasteners to secure the spoiler. Start with the outside bolts first.
If you plan to put a decal on it - for a level fit and trust me on this - measure from the bottom letters of the decal to the bottom of the spoiler.
Enjoy and send me a pic sometime and tell others about them. I have only a few left and that's it for a few years. - Jon
Here's a pic, not mine but one Jon sent to me