Chin spoiler?!

67/68 Camaro is probably the easiest. You can get a plastic version from OER for $35, so if it doesn't work you're not out much money. I put one on my Duster, once you get past the "camaro" part it looks pretty good. :D They're pretty generic, and can be modified pretty easily. If you want to get really crazy you can reshape them a bit with a heat gun too.

http://www.summitracing.com/parts/oer-3916673/overview/make/chevrolet/model/camaro