I don't know about transportation, but the sterling has seen some use in solar power
The Energy Blog: About Dish/Engine Concentrating Solar Power
Also, not sure the volt will be at 40% once you get the power to the axles, I haven't seen anything but speculation there, and don't know of any super efficient CVTs for that matter.
Edit: found a whole DIY Sterling engine deal, little nicer looking than the tin can approach perhaps:
http://www.solarheatengines.com/