I've seen pics of a VW TDI Diesel (1.9l 4cyl) in a hardtail chopper frame, running through an HD style trans. It wasn't pretty, but it looked good for what it was. I'm sure all you'd ever see of it on the road is a speck in the distance and a cloud of smoke. I bet it'd get 60 mpg too.

There is no greater thrill than being shot at with no consequence. -Churchill