I've got a muffler from a ZG in the garage and it doesn't have a lot in the way of baffling. If you're looking for more sound you'll probably have to ditch the whole stock system as the collector chambers upstream of the mufflers probably do more for sound restriction than anything else.
On another note: I'll start taking "Loud Pipes Save Lives" folks more seriously as soon as I see one riding a bike with the pipes aimed forward.
Good Luck
Bill
1947 Indian Chief, 1968 BSA Shooting Star, 1970 BSA 650 Lightning, 1974 Kawasaki W3, 1976 KZ900 A4, 1979 KZ750 B4, 1979 KZ750 B4 Trike, 1980 KZ550, 1981 KZ1300, 1982 KZ1100 Spectre, 1985 Kawasaki ZN1300, 1987 Yamaha Trail Way, 2000 Honda Valkyrie Tourer, 1981 GL 1100, 2009 Yamaha RoadLiner S