I have recommended The Muffler Shop in the past. They do good work and decent pricing. However it depends on which one and what kind of work. The one on Hull st. seems more expensive than the one on Horsepen rd. The one in the west end charged me less to have the cutout welded in on the Z/28 and my cutouts on my old exhaust on the Cobra.

They wanted to charge me 50 bucks to tack weld on some turn downs for my dumps. I had Meineke (Hull St & N Baileys bridge) Fab me a set instead from 16 guage galvanaized and weld them on and paint them for 20 bucks total.

I recommend both shops, plus the guy at Meineke does custom exhaust there on the side(H pipes, x pipes, etc).