I hate to burst your bubble, but if the car is in the USA it wouldn't be breaking any law whatsoever. Fish are not protected under law in the states.Because they would be breaking the law for that one since its over the engine and can cause lots of heat. Which breaks the law of Animal Cruelty.
Maybe you should add this tank to your list...
Tank currently selling on ebay
I would be willing to bet that if you peer under the tank there are pipes in and out of the tank/car so that it is plumbed into part of the central filtration system they have there.
the car doesn't provide a natural habbitat though. its like, a human living under the ocean, it's just not right. i try to provide a natural envirorment for all my fish, it's just better that way.