Here is a link to a Swedish company that recently built a prototype series-hybrid stirling electric car.
http://www.precer.se/Files/Precer_Data_Sheet_D.pdf
A lot of the commercial Stirling businness is coming from Sweden today.
http://www.cleanergy.com/technology/ has the old V161 engine in production (9 kW electrical output + 25 kW thermal) and it is used both for gas and solar powered applications.
United Stirling did some prototypes together with car companies during the oil crisis in the seventies. They had working engines in the 60 - 80 hp range.
Here is a paper with a lot of info on automotive stirling implementations.
http://mac6.ma.psu.edu/stirling/repo...1997021349.pdf