Note that the Greedy Greenies haven't jumped on Bush's proposal. However, I'd just love to stick it to the Saudis, so bring on the hydrogen in quantities that make it affordable. The arabs can keep their oil and eat it.
Where can I get my car modified?
Since you lose at least 30% in the conversion to H2, I think that the price would be much higher.
I haven't done it myself, but I knew a guy that did it in his garage, and as I understand it, very little engine modification is necessary. Used a Camaro--lost about half the horsepower and the range of the car wasn't what it was, but as I recall, the only major modifications he did was added a storage tank for the hydrogen.
Of course, you do run the problem of "cracking" the hydrogen (as the article puts it) in your garage. Hydrogen can be dangerous stuff, and I don't think your insurance agent would take too kindly to filing a report about how you blew up your garage...
Try your local State University's Physics Lab. That is after you take out your back seat.