Mine came from Heffner... yea, it was kinda' pricey, but I'm really happy with the results. I had an opportunity to purchase one from another vendor for considerably less, but I was not confident in their tune-up reflash, hence my decision to go with the Heffner version.
I suspect Heffner has done more GTs than anyone else...
I've heard nothing but good things about 'em, and remember the only thing that travels faster than a Ford GT, is information on the 'net about poor customer service, unsatisfied customers, and unimpresssive performance.
Heffner's operation seem to be mostly free of these kinda' issues, unlike a few others that I've heard about.
mardyn