There is a shop, that until recently only took late model mustangs as clients. They have since merged with another shop and are building and tuning all American cars and trucks of all years.
They have some of the best tuners in the country. There shop consists of 2 in floor dyno's and 11 lifts. Not only are they great at their jobs they are stand-up people.
Their webpage is still mainly mustang specific but don't let that discourage you from taking any American brand to them.
http://www.modularpowerhouse.com/contact_us.php
Phone Number - (770) 591-0000
Fax Number - (770)-591-0996
21 Curtis Court, Bldg 10
Cartersville, Ga 30120
I do not work for MPH Performance but have been a long time customer of theirs. They do superb work and are great people in general.
They have won the 5.0 Magazine King of the Street Competition 2 of the 3 times they have entered. They build amazing cars.