Joe is correct on the armrests.
The fold down rear seat was available to order on any 67-69 Camaro, regardless of model or year. Option A67 was ordered for 4,397 Camaros in 69. I would suspect people ordering lot of options would pair a deluxe interior with a fold down rear seat, but it was not mandatory.
If your Z has one, congrats!
If not, then keep the full width rear seat. Adding fold down rear seats are a bit of a pain and require welding brackets to the floor and channel to the back bracing.
