I don't see how there would be a lot of a problem except for powering it. You could do that with one of those 7200 watt adapter things for vehicles. Wire that mug straight to the battery and you're set as far as that goes. Keeping the xbox so that it doesn't kill hard drives is a problem I've heard, you might want to find somebody that has done an in car mod and ask them how they did that.
Yea, too much rumble on the hard drive kills it, I know you have to pad it but I dont know how or with what.