I have a buddy with a 70 Challenger 440-6 car that went with a TTI 3" system with the 3" x 16" Super Turbos. Exhaust sounded great for about the first two years. Then, the fiberglass mat started going away inside the ST mufflers & now the car is so loud, it's almost unbearable to drive or ride in.

My suggestion would be to replace with different mufflers & add a pair of GOOD quality glasspack-type mufflers (resonators) that have a body length of 18" at the rears. If you can't find something, I can build you the resonators. 3" dual exhaust is LOUD - there's no two ways about it. Also, you don't really need dual 3" exhaust unless you are over 500 HP, & even at that you can run dual 2.5". I have customers with 800 HP running dual 2.5" & they don't notice loss in HP or flow until they go over 4800 RPM.