Google's your friend when calculating your elevation above sea level. The stock main jet in your Blaster is a 230. I would run a 250 main and see how your plug looks. A 240 may be just fine, but its better to be richer than sorry.
Also, is your airbox lid still installed? If so, the 240 main will be plenty. If not, definately run the 250 main if not bump it to a 260.