Found this interesting
 

https://www.autobloggreen.com/2009/05...lec/#continued

the opel kadett is the european version of a chevette. shame nothing ever came of it...

but just goes to show theyve been thinking about hybrids for a very long time

I've read about some of those concepts. Nobody could come up with a way to give the power needed from a Stirling engine that people demanded. It can't be directly coupled to the transmission because it doesn't rev well but that idea looks like it could work. Especially with the tech we have today.