Very interesting thread - I've just been making inquiry on the same idea - for my Aussie Charger A body.
1st - the original AAR mufflers flow like crap...but there is a good, great sounding alternative, made by Dynomax (forget the Flowmaster - too expensive and sounds like a Chev)
2nd - you need to decide if you want the original AAR tips with the diffuser (which restricts flow) or the 2.25" offering also from Accurate that has no diffuser.
Here's what I found out from a guy who makes mufflers -