Hi Kevin, welcome to the site and congratulations on acquiring a 6x6 Hustler! Try
http://www.tiresunlimited.com for the common 22" rawhide III tires or look around the site and see what others are running if you want a tire specifically for mud or just for water, etc.
As for the identification, I will have to let one of the Hustler experts chime in on that. A lot of them are at the Ledges ride this weekend but I'm sure someone will chime in when they get back.