If you are in southeastern N.C. there are a few shops here, Waynes Dyno in Jacksonville is a speed shop and a Dyno-Tune shop in one. (That's where my custom chip and dyno work was done) My personal choice is Anderson Motorsports just outside of Wilmington. It's a small shop, that has personal customer service with a outstanding owner with a LARGE amount of experiance with pushrod and mod motors. Over 20 years in the game and continued repeat customers. This is where I get ALL my work done at, I would not take it to anybody else, PERIOD. He is honest, fair, and he knows what the he** he is doing. Great prices too.
Custom Performance is located right behind Lowes Motor Speedway. Then you can drive a 1/4 mile over to the track and see if your stang will beat Tony Stewart! http://www.gofastfords.com/ I like their domain name Go Fast Fords!
Watch out though, they'll put a license plate frame on your car if they do any work for you (cool) and then no one, I mean no one will race you (not cool but funny).