Muffler-can keep kinda quiet sounds off at rpm

I know this has been beato death
I need to select mufflers for my 70 Dart
360 mag with 340 and magnum manifolds 2 1/2 run the length of the car exiting at the bumper
I’m really wanting mufflers that I can keep fairly quiet but that sound off when thrashing the car
I’m looking at ultra flow welded
Any ideas