I can deadlift in the low 400's no problem, but there is no way i can pick up the back of a car, not even a small one. I guess it has alot to do with getting a good grip and proper leverage.
I remember watching pumping iron and Franco moving a small car that had been jammed too close in a parallel car park. I know he could dead 700-800 lbs or something. So I'm guessing you need to have a dead of at least 600 to lift a car.