Seems the highest MPG cars ever sold in the USA were carburetored.. The Honda CRX, like the one I just got, is carbed and is rated at 57mpg in the 1987 CRX sales brochures.
the 4wheel drive may be a slight drawback, but ive seen 4wd trucks modified to 2 wheel drive (front wheel drive), some even using the rear drive shaft as a Power Take Off unit..
I went the route of buying a different car, but then again I'm a experimenter at heart and wanter to start with the best I could get.. aka a CRX.. Also i dint have anything really decent 2 work with that i didnt mind chopping up to much, I have a decent car to ecomod with that has a 5 speed stick and is a 4 cylinder but I wasnt going to start chopping up my 06 chevy colorado pickup