Yeah, Modular Powerhouse is one of the premier Modular engine builders in the country, they are about 50 miles south of you in Cartersville, Ga. Straight shot down the interstate from Dalton
I was going to mention Modular Powerhouse as well.
MV Performance in Statham, GA is another good choice. Tim Matherly has been in the Mustang racing scene for quite some time and has more than a few wins to his name.
I've got a buddy in Adairsville, GA that graduated from NADC with me. He's been working on cars for over 10 years. He wouldn't be a better choice for building engines or tuning such as MPH, but if you're looking at doing some smaller things, he'd do some good work and save you some cash. PM if you want his info.