Offset in, center out/or dual out. Some shops and people in the know call it a 'side/center muffler'.
Are you getting all new piping? Exits are all up to you like Trent said. Stock single outlet in stock locationi, single out the side in front of the tire, duals angled, straight out angled....etcblahblah.
Here's mine...I did it a bit different. The muffler is a Flowmaster Super 44 w/ 3" offset in/dual 2.5" out....but I'm running 2.5" piping coming in, dual 2.25" out. Dumped at the spare tire carrier. I wanted mine all nice and neatly tucked up and away from anything. I didn't want no damn driveshaft rubbing muffler BS....so as you can see.....it's all about the installer and his skills with a bender.
For your 3.0....I wouldn't go any bigger than 2.25" on the piping if going single exhaust.