One vehicle I haven't seen mentioned is the XR3. I've got the plans, and intend to build one, if I can ever get the Kubota D902 diesel engine. (3 cyl 23hp) I might build it and bolt a small gas lawnmower engine to it to start. $500 vs $3000 for just the new engine.
125mpg supposedly on diesel only. Can be hybrid or all electric. Good plans. Helpful group of fellow builders.
Lets see if this link to a pic loads.
The website for the XR3
Michael