The service manual doesn't mention the differential as a jack point but it does recommend against using the suspension.

The service manual has a diagram in the frame section. I'm assuming that all of the pieces in that diagram are "frame rails." I just can't seem to match the diagram to any visible components on the car. The service manual does say that the "Body Code plate" is attached to the "top of the right frame rail" in the engine compartment. If I can find that, it may offer a clue.