I bought a used one off of Ohio Mustang supply for my 73-he deals almost excusively big bodies. We'e made two trips out to his place for parts so far-including one for a full rear quarter & wheel well!!
Edit: site link:
http://www.ohiomustang.com/ Ok, so he's added a lot of other stuff! When I first bought stuff from him it was a few years ago and it was a little start up selling mostly through ebay. Nice guy, his name is Don. I'd bet he's got something for you, dont know about the shipping charges though....