I cannot stand the Flowmaster sound. They're just way too loud and obnoxious. There are a LOT better flowing and sounding mufflers on the market nowadays. But it's yours man. Fix it like you want to.
My 72 duster had a 2.5in 30 series Flowmaster on a built up slant six. Both of my Jeeps have 2.5in flowmaster 30 series. I am a flowmaster loyalist. The only things in my driveway not running flowmaster is my VW's.
And I love the sound. As long as its not too big to create a raspy exhaust sound.