Hi Greg,
From what I can figure out the FE/FC had the sockets (Retainer,Cover, Spring--Rear Seat Back) without the locking arms, and the FB/EK station sedans had the sockets with the locking arms, being safer for the rear seat passengers, depending on what else you had in the back. The master parts catalogue I have does not have a different part number for these but the rubber part has a bit cut out where the arm is on the FB/EK one, but is the same part number on the FE/FC ones. Also the FE/FC ones are not left or right handed but the FB/EK ones are.
Just my opinion, hope this helps
Cheers Stewy