muffler case size

I have Flowmaster 50 Series Delta Flows under my Cuda. They are 4" thick, 9.5" wide and 17" long. I have 2.5" offset in and 2.5" center out. These are resonably quite at cruise with no resonance but have a nice bark at WOT.

Don't get hung up on individual muffler flow numbers. All performance mufflers flow more than the engine produces. Make your choice on sound.