Try
www.mustangexhaust.com. They have a bunch of sound clips their for you to listen to. I don't know if there is a need to go over 2.5" on the exhaust with the 5.0. As for free flowing mufflers, I went with magnapacks. Dynomax, Borla, SLP... all seem to have similair flow through designs. I would stay away from chambered mufflers if flow is what you are worried about. That includes flowmaster, Mac... etc.
Tha magnapacks are great by the way. Sounds awesome and doesn't drone like flowmasters. Stainless steel for that kind of money isn't a bad thing either
