I have been lurking in the shadows here for about a year...having joined shortly after acquiring 521. I've taken note of many others contributions and it's time I do a little myself.
521 was ordered by Larry Miller for the Ford Racing School at MMP, one of a pair of cars used for promotions, hot laps and track use in general. It's prominently featured in the latest edition of the Shelby registry as it first appeared new with Tom Kirkham at the wheel. According to him it is the second most documented build with over 400 photos while being constructed at the factory and a few hundred more taken between 2007 and 2012.
The first 7500 miles were not the easiest on this car...it was rather abused when I first looked it over. Scratched and dinged body, bald tires, & cracked windshield was just the tip of the iceberg for damage it sustained in 2500 track miles. (Odd how every person who ever drove it recalls being patient and easy on the car.)
I'll post some images here showing it new, during some of its use before and after becoming the latest caretaker and of the restoration. Perhaps some of what I unearthed in the process will assist you in heading off issues before they get bigger in your own car.