I am looking to do the same thing with our X1100Cs. The problem is finding a stock height automotive tire that will fit the 12" wheel. We did this with our Bobcat 3600s and Gators. For the Bobcats I bought 14" ATV wheels from Summit Racing and used Starfire trailer tires. The Gators used trailer wheels and tires. If I measured correctly the bolt pattern is 4x110. The parts lookup shows the HDWS wheels as 8.5" wide and a quick measurement without removing the wheel and tire showed about 6+2.5???? Not 100% So a 4x110 5+3 with the proper weight rating should work fine. It may stick out a bit further than stock but the front looks like it has plenty of room.
But one possible problem is the bolt/stud design of the hub. The factory Kubota lugnut/lugbolt head is too big to fit into the recessed holes of the aluminum wheels I have for the Bobcats so you may have to find a steel wheel with no recesses.
When looking for new wheels, as well as tires, you need to make sure they are rated for the GVWR of the vehicle divided by 4. This is why I had to buy fancy aluminum ATV wheels because I could not find steel wheels that would fit the Polaris 4x156 bolt pattern that were rated heavy enough for the Bobcat plus driver.
The stock HDWS tires on the Kubota are rated at 1675lbs at 10mph. So that will give you are total rating of 6700 lbs. The GVWR is 3,999 lbs. Plenty of room to spare. I would also like to find a better wearing 12" radial to run in the winter but the weight ratings are killing me, none are high enough. Best I found in 25x10-12 are Carlisle Versa Trails at 1200lbs, which will work, but I want more of a truck tread.
Sorry for the long post but I have been researching this topic for many years now and have yet to come up with a perfect solution. Luckily the new Gator we are getting is coming with the factory 14" aluminum wheels so finding an automotive tire for that will be easy.