The Cambridge was the less expensive model and the Cranbrook was the better one. The Cambridge came with plain gray cloth door panels with burgundy vinyl at the bottom. The Cranbrook came with two-tone door panels separated by a shiny plastic strip. The top part had stripes and the bottom part was solid-color vinyl with embossed lines to make a box design. I've seen the door panels in blue, gray, and green depending on the outside color of the car. Another thing that shows it's a Cranbrook is the courtesy light switch on the upper hinge of the right front door. It's actually a modified hinge screw with a pin-switch in the middle of it.
After all this rambling, I remembered the sure-fire way to tell what model it is: Look on the firewall for the body number tag. If the number begins with a 100, you've got a Cambridge. If it's 105 you've got a Cranbrook. The VIN on the driver's door hinge post also has a different sequence depending on the model.
I've had a bunch of these cars and like them a lot. Hope this helps.
Harold