Tom has shared some excellent points. We have all heard horror stories about folks who went to what appeared to be reputable shops (but evidently lacking in experience)--our own Website Leader is one who suffered in such a situation.
In my case--I wanted someone close to help with tuning, etc. down the road and I got lucky right here in Fresno, which has always been a key location in California motorsports (believe it or not). I knew Joe Boghosian was known for building Indy motors, AA/Fuelers and can put together Drakes and Offys like nobody else. But then I found out he's been keeping Dick Smith happier than a dung beatle in sh...(well, you get the idea) by keeping his original, but well used, puppy running as good as it ever has for the past 30 or so years. In fact--he's building Dick a new monster, and mine is hopefully next in line. Our parts are laying on the bench next to each other.
George Anderson, a virtual immortal living in the distant Olympus of Nebraska, and others are out there. The good ones are busy--they're not cheap and you may have to stand in line. But if you're going to spending the bucks to have someone build you, as Tom puts it, the biggest component of your Cobra, you're not going to mind waiting. It's damn near a dead heat between the Poles/Mormons building the car, and the Armenian building the engine timewise. Course--the time has come to wake up Kee for the trans...