Are your resonators rusting out also?
Yes - custom is the only route...
I'd punch out the pre-cats, delete the rear muffler, redo exhaust pipe, replace resonators with magnaflows. Then you either do turn downs after the magnaflows or pipe it out the back where the rear suitcase used to be (which will be less smelly than turn downs).
You can always add a rear muffler later if this is too loud.
Below is magnaflows, no rear muffler, turn downs - sounds great if you ask me
[youtube]
http://www.youtube.com/watch?v=31Fl5sRvS84[/youtube]