There is a group purchase going on at FFCobra of 24" long Lobak spiral mufflers:
http://www.ffcobra.com/ubb/ultimateb...c;f=1;t=039055
Some pictures are at:
http://www.ffcobra.com/ubb/ultimateb...c;f=1;t=038738
You just cut out your old glasspack and weld in the new one. RPM also sells a 20" version (not part of the group purchase though).
-Stu