Yes, lockers are required or at a minimum highly recommended unless you have tons of articulation which Montero's don't up front. You should also have ample amount of armor (unless you don't like the state of your undercarrage or rocker panels). 33" tires are highly recommended as well for added clearance although some have made it through with 31's although their rigs will NEVER be the same without a copious amount of metal bending.
That said, I did make it through the 'con in my old v6 4 door gen I with a properly working LSD in back, a couple of straps through the tougher obstacles and a relative amount of rock stacking as needed.