Do you need doors or can they be reskinned? Several Mustang parts vendors sell door skins which allows you to replace the outside portion with a good surface. You just need a good body man who can accomplish it for you. You can find them at http://www.texasmustang.com
If The doors are beyond being repaired with new skins you might try Mike Jenniges at 512-288-2569. He's located in the Austin, TX area, works on nothing but old Mustangs and has quite a few parts cars. If he doesn't have the doors he may be able to give you the names of some one who does. Good Luck on the 'Stang.