I don't know if you can do so on all mtbs, but we have done so on at least one. You'll need new brake levers too, I think, because v-brakes pull more cable than calipers. New brakes are cheap, even cheaper if you buy used. Go for it. Reviving old bikes is so much fun :-)
PS. If you have a mtb with v-brakes already you can check, by just switching over a brake and seeing if you can get the brake pad to hit at the right spot. Brakes are really easy to move around and adjust, if you just pay attention to what you're doing and take pictures every now and then it's hard to do anything wrong.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett