They would definitely need to devise some sort of safe container, not only because the hydrogen burns quite well, but also because in order to contain enough H2 to fuel a vehicle of today's standards, the hydrogen gas would have to be under considerable pressure.

I personally would stay away from the kit. Hydrogen is still in alpha when it comes to cars.

Close to the topic, toyota made the first hydrogen powered car quite a while ago. Pure hydrogen. But it doesn't use it in a fuel cell engine, the one that is so famous for having water as a by-product. Instead, they burn the hydrogen in a close to conventional way. It is still more efficient than petrol/gas/diesel, but it doesn't reduce emissions by much. What's that about?

Another thing that is over-hyped about hydrogen as an energy source is that it isn't an energy source. It's a storage.

I say that as soon as oil becomes too expensive, people will actually start caring about mileage, and that will start the avalanche

-K