In Connecticut I would recomend Custom Muffler Of Enfield. You can call 860.741.4344 Adrian is the guys name and he has a great reputation. I know in our area he does alot of Hot Rod stuff.
You can try Paul Hetherington who owns the Meineke shop in Tewksbury M***. He is a rodder and has done nice custom systems for some friends. Prices are reasonable. Give him a call or drive by (if the car is currently driveable) and he can look at it and give you an estimate.
Jay's Custom Exhaust is the best shop in the Merrimack valley area. Jay's Custom Exhaust 113 Congress Street Lowell, Ma 10852 Phone 978-441-9248 Jay does exhaust only and works by appointment. Contact can be made after 3:00 PM. Joe Szafran