So...you need a ~1.5l econo donor car that's at least OBD2 with relatively low miles or a freshly rebuilt engine...
Find something that's been re-ended. Maybe a Yaris or something similar? Be sure to either check out BSFC maps or at least typical fuel consumption.
BTW, unless it's running on propane or the like, a genset will pollute more than a typical car...though maybe not more than your old diesel .
