Read and weep...
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1205292181GS450 for the rear should be direct swap out, same axle, same rubber dampers on the drive side, same drum brake on the other. oops forgot, rear is a 16" rim, still works though and might give some more options on tires. If you go to 130's, you can use harley tires which have deeper tread.
on the front you got some options from GS450 to 750 all use the same size.
Double check the tire size
Pick the spoke pattern and go for it.