You can buy bars pretty easy, but most guys just build their own. As long as you have some sort of welding skills it simple. Just got to a Tractor supply and buy 2 3 point hitch bars, cut them in half and slid them inside of some 2" 1/4 wall tubing ( I think ) and weld it all up.
As for tires, STS's are nice, but Ive heard they dont last long. If you have good tread on the A/T's they should be fine. You only limiting factor is the size, not optimal, but doable.
Oh and i hope you have a double disc clutch!