Steve,
I checked Desert Valley Auto Parts, and they have a slew of firebirds in the yard. If you contact them and they are willing to cut the bottom off the fender you need, let me know and I can pick it up and get it shipped for you, or if they will only sell a full fender, we can find one that is damaged in front and I can cut it down and get it shipped. Let me know if you want to go that route. Here is a link to the search page where you can check the Firebirds they have in the yard and see pics of them:
http://www.dvautoparts.com/