If you are intending to conduct a true restoration, then you have more than just the starter to concern yourself with.
The original engine came with a Starter/Generator that needed a 4 terminal voltage regulator to recharge the battery. If you have a later (post 78 Kohler) engine that has a dedicated starter, then it should also have an stator coil mounted behind the flywheel, feeding a rectifier/regulator. The wiring harness would have been altered drastically to go from one system to the other. You can find the Parts Manual for you tractor in our Tech Library. That will show you how your tractor should be wired. d
Used Start/Gen units can be bought off of e-Bay from reputable Sellers like Joe's Outdoor Power, as can used regulators. I think that you will have to make a new harness for your tractor but first you need to determine what's different between your tractor and how it was before the alteration.