Eddie,
what Tom says is true, about the burning out. The Super Turbo are fiberglass lined and it toasted this fiberglass so bad it busted the seam where the muffler was joined together. I've never seen anything like it.
I would at least have 2 feet or so between the cat and muffler, more the better. As far as what it will sound like, it has the most to do with muffler type and pipe size.
What I have is my Edelbrock TES headers, with the y-pipe of course. The y-pipe comes with an adapter pipe to adapt it from 3" (what the main y-pipe ends with), to the 2-1/4" tailpipe, or stock cat size. So left the adapter off and had a piece of 3" pipe go to my 3" in/out cat. Cat is in stock location so the heat shield still protects my floor. On the exit end of the cat, I had the Flowmaster y-collector welded to the cat, in reverse. The y-collector is made to feed two pipes into one. I'm using it to feed one into two. The y-collector is 3" in, dual 2-1/2" out. So then I ran two 2-1/2" pipes over the axle out the back. One goes straight back, the other goes over the end of the driveshaft to the other side. Not enough room to have two pipes go back on one side.
