I have 4 cars and the 67 Mustang I am doing is strictly low budget, so I didnt go for a pricier system like Flowmaster, and after a little comparison wound up with a set of Flow Tech headers, and a Heartthrob 2 1/4" dual exhaust system, along with Eliminator mufflers for my 67 289 coupe.
I bolted the headers on in about 15 minutes, welded the PS bracket on in about 20, and took a couple of hours to install the dual exhaust system, and I couldnt be happier. It was cheap, the Elimanators have just the sound i was looking for and all i have to do is cut the ends of the pipes when time comes to put my chrome tips on, after the paint job.
Cost was about $275.00 for everything.