You might think of making a short list of shops by checking with the Better Business Bureau. At least you'll know where not to go. I'd stay away from collision shops as they usually work on a quick turnover and mostly late model cars.
Have you checked with the local Mustang clubs? Also check the yellow pages under automotive restoration and then check with the BBB. In cases like this, you usually get what you pay for. The apperance of the shop will tell you a lot, too.
How about the Ba-Da-Bing body shop? Sorry, that's the wrong kind of body. Good luck | 
Body/Paint Shop 
