Limitless Performance & Fabrication on the north east side of town or Midnight Performance on the north west side of town. Between those two, they pretty much run the Houston mustang show. Or if you don't mind a drive, Triangle Speed Shop in Orange, Tx is real solid.
Triangle speed shop.
Chris car doc( may have a long wait and charge more, but worth it).
Houston performance ( on 529) ask for Chris- this is the shop I use for my terminator and gt500