POS mule 550

I have a Mule 550, what year I do not know. It is completely stock as far as I know. It has the original 10" wheels and I would like to upgrade to a 12" because I need to run more asphalt friendly tires. If there is harder tire available for the 10" wheels, PLEASE let me know. My question is what do I need to know to order the correct wheel size and tire size to make this swap. Links to dealers with these options would be greatly appreciated.