1970 318 duster exhaust question???

I had dual exhaust set up on the factory manifolds of a '71 Dart, they worked and sounded fantastic (Mel & Sons, Concord, CA), I don't remember what mufflers I used but they were a common manufacture and not too loud, just loud enough for people to notice. I thought you couldn't get anything but exhaust systems for headers though, my 16 year old is looking for something similar.
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