Find yourself one of these
:
I've got a stroker 1776 on the bench (the famous Mileage Motor) that would push this to 50mpg at some speed >60mph. It would do 90 mph with 25hp.
Since I haven't scored one of the two in existence (
) I've settled on this:
The Audi/Passat/Dasher body in the three-door bodystyle, with a longitudinal diesel and a five-speed. If the money were to show up unexpectedly, I'd make it a mild hybrid with a Buick altermotor. Then add the turbo.