If you want the ultimate Microcar, then get a Fisher Fury. Shove a Hayabusa motorcycle engine in it(as is very common), and you'd have what is basically a motorcycle on wheels with better aero. 0-60 in ~3.5 seconds, 50+ mpg, 160+ mph top speed, 900 pounds curb weight, corners almost like a Formula race car...
Makes the Honda Beat look fat!