Good thing there was a lack of red lights back then, stop too long & have roasted nuts. That's most likely why they wanted something that would go at least 40MPH.
I knew it was possible! That's it - I'm building one!
Could make a boiler out of coiled copper line. Wouldn't need much water. Then put a little propane burner under it & hook up those little 1lb camping bottles. Now if I could only build an engine ....
Cancel that engine Smitty your well on your way to being able to produce your own er ah fuel. Then once you have figured out the proof er ah octane then you can start on an engine to burn it in.