The Quiet Flowmaster?

I have 50 series delta flows behind my ~375HP 360 with 2.5" pipes and a X-cross over. I have virtually no interior resonance and the car is quiet enough at cruising speeds to carry on a conversation comfortably. This set up is much quieter than the dual 18" glass-paks that I had behind the \6 that was previously in the car.

I also have a 50 series delta flow SUV muffler (thicker than a standar 50 series) on my Dakota and inside the cab it's no louder than stock.

If you want something quieter the 70 series big block muffler would likely be the way to go.