[Stan]

I read a technical paper recently where the researchers improved the FE of a late-model TDi just 2% by removing about 250 lbs from the car. In contrast, reprogramming the chip yielded 4%.

OTOH, one CAN get 70 mpg from an old Mk1 dwiesel radjit...

Start by reading this Ecomodder thread and the linked article about the "Rabbit Sipster". Forget transplanting a TDi into it...just apply the aero mods he does and I bet 70 mpg is not out of the question. Heck, I used to get 50+ mpg from my first-gen Rabbit and Pickup both just by using a light foot.