Without some pretty good amount of work, there is only one tiller that will fit on the GT, none for the SGT.
The tiller for the SGT requires 3pt and rear PTO.
The tiller that fits the GT has it's own engine and needs either a sleeve hitch, or rear 3pt. You can adapt an older tiller (#1, 1A, 2, 2B) to work but it takes quite a bit of mods. I've done it.
Here's the thread.