Any seat, given its width and length measurements will match up with your GS frame, can be put on a GS bike. The GS frames, at least the 550's for sure, are a standard flat-top rear frame design. Attaching it is your choice. It'd be quite simple to weld on some basic little tabs and just use bolts, some people have gone out of the way to retain the factory seat hinges so it still flips up, others just cut all that crap off and bolt it on with a couple bolts. I can take frame measurements of the front(behind the tank) to where it widens out to the rear if you want, or just grab a tape measure haha.
Just compare measurements, width and length, with where you'd cut your frame/end your frame, and see if it'll fit. Either way, ANY aftermarket seat you buy to make it look like a cafe, bobber, whatever, is going to require minor modifications to either the seat or the frame to "bolt on".
Will
