On the 250x you will have to get your hands on a 300ex crank (longer stroke) to get the full 330ccs from this kit. I believe the kit uses 11:1 compression which means you won't have to run race gas. If you want to take advantage of the extra speed you will need a rev box.
With this kit it will most likely break down oil more often which means it will need to be changed more frequently.
Oh yeah i believe it uses a Weisco piston, but i think it really depends on where you buy the kit from.
2007 can am outlander 800