robriley

yes, you can do it but i'm not sure what all is involved as far as parts. I know that some of the parts on the volcano s/v are different than on the volcano s-2 (which comes with the 2 speed).
one thing to consider tho, is that a 2 speed is not really the way to go if you plan on running it off road all the time. 2 speeds are best used in on road cars & trucks. the problem is that when you are off road, and lets say that you'r climbing a hill. the truck will go up the hill, and then it will shift into 2nd gear. the rpms will drop as well as the torque, so the truck may actually slow down and struggle to get the rest of the way up the hill.
It just depends on how you want to run it i guess. Most off road trucks benefit from a single speed trans to keep the rpms and torque in the upper range.