in terms of finding a parts car or trying to visit a junk yard I would suggest looking on partingout.com
where salvage yards are parting out whole cars. if the mustang year you need isn't listed you can create a parts wanted listing - I used this tool to find a thin piece of chrome and it I had to offers to sell and choose the one closes to me. I don't think I would have ever been able to go to a junk yard and ask "hey do you have that little piece of chrom on the hood for ...." it just doesn't work like that.
Anyways I think you could use it, good luck