Central Oklahoma is saturated with Mustang shops. Here is a list of shops in the OKC metro area that use Mustangs are their primary source of business with a little description that is my honest opinion:
Oklahoma Performance Automotive - large operation; has a large following; tons of positive feedback; shop is always packed with business; shop car is a nitrous car that runs 10s N/A; they own a Dynojet; fair prices and I'd rate them as an honest shop
SW Tuning - small/medium sized shop; very clean; high attention to detail (perfectionist); specializes in tuning (people travel from other states for his tuning); owns a Mustang Dyno; extremely honest to the point of being blunt (not a "tell you what you want to hear" business); some say prices may be slightly high (probably in comparision to cheap competition, not necessarily in general), but the shop stays busy; owner is easily one of the top two most technically intelligent people I've ever met in person
B&R Automotive - major operation; large shop; a large portion of their business is street racers; has the majority of the big HP business in the metro; shop car is a 7sec drag radial True Street car; often complaints that they are very slow workers, but it's hard to ignore the performance that leaves their shop
Elite Auto - small shop; very personal; does a TON of powder coating at the shop; builds custom turbo kits; honest guy; fair prices
SB Motorsports - small shop; by appointment only; does not do general work; only works on extreme street cars or street classed race cars; gets paid what he's worth i.e. NOT cheap; waiting list; honest guy; very, very good at what he does
HP Performance - nice, large facility; they do everything; have a 7sec car that they detuned to 1000rwhp or so to street race; owns a Mustang Dyno; does not have a good following/reputation from mainstream Mustang owners; many rumors about certain things going on, legal trouble and claims of ripping people off yet they still get business (but I don't know how)
RPM Racing - large shop; been there a long time; extremely incompetent; endless amounts of pissed off former customers that had their "learning experience" with this place
Powerhouse Performance - large shop; combined with an import shop (rumored merger was to keep from closing); makes RPM Racing look smart; billions of reports of dishonesty; often referred to as the punchline of Mustang shops
Those are just the Mustang shops. There are also general domestic performance shops too. And understand, my business is a warehouse distributor to 90% of the performance shops in the state and I am big in the Mustang scene in these parts. These descriptions would be rated extremely accurate by an overwhelming majority of experienced Mustang owners in this area.