I am in Canada (Victoria, BC), about 2 hours from Vancouver. I've had a few friends who have sold their diesel rabbits to US citizens, and the vehicle basically has to pass an inspection before it can be registered. I haven't heard of any problems; just made sure the car will pass an inspection (no floor holes, structural rust, etc) and you should be fine. Both times I know of, the car was towed down and then registered. It's a lot more work to try to insure it here with a temp pass and get it across the border.
Don