ok not much to go by here but the pic: http://webhost.bridgew.edu/jtyks/ebay/DSC01005.JPG
do you think it will fit on a GS without too much trouble? maybe just grinding out the lower linkage? I really have no idea, especially with that attacked resivoir; but I can get it dirt cheap locally. The seller bought it from the SVriders forum and "thinks" it's from an '01 GSX-R 750.
well... ANYTHING will fit with enough modification.
That resevoir will require cutting the airbox if it's still in, or replacing it with a pod or lunchbox type filter. It looks like a pretty long shock, probably in the range of 330mm. Compare that to the GSes 292mm and you've got 4cm (1.5 in) of rise in the shock, which should sit the tail around 3 inches higher, minimum. That's a pretty serious change in steering geometry. You can fix that by changing the length of the dogbones or modifying the linkage, but that's messing with "leverage ratios" and is generally not a fun thing to do.
No matter what, you'll have to lengthen your sidestand in order for it to work. The GSes short one just won't cut it with that sort of change.