Any Case dealer who participates in the Megavolt rebuild program has access to the starters. Probably a good local independant rebuilder can fix you up also. As I previously stated, beware of cheap imitations, they are identical in appearance but wound lighter in the armature and fields. They are sold by some shortline outfits, I believe that Tisco is a knockoff for instance.
Be aware that you may have trouble getting a core charge for your old starter since you do not have an identical trade in but the core value will not kill you if you don't get it.
I do not have to tell you that your location will require the heaviest battery that can be fitted and all cabling first rate and I would cable the battery ground right to a starter retaining bolt.
As previous, the 580 D series ( a 207 CID) is the last series to use the three bolt Nippondenso starter, all the internal parts to the tractor are the same as the Delco setup so the only changes you will have to make are external, such as slightly bending the steering pump pipes to get installation clearance. At first look you will say "it won't fit" the drive is larger but it will and you will not be disappointed.
Check with Case first ---580D gear reduction starter---. If they do not have a rebuild program you may have to go outside them to get a more reasonable price. just be sure of the quality.
Mel