Not a budget project. Those are fairly pricey components compared to everything that's available for building an electric 2-wheeler.
I'm planning to build a whole vehicle for just the amount of money he probably spent on the Alltrax and motor.
I've been thinking of doing something like that to a old bike frame I have. But, it would probably need some kind of registration before hitting the road. I guess that's the advantage of using a previously titled vehicle.