I'm a little confused since you mention reclining and non-reclining in your original question.
I'll use your 300SD as the model (non-reclining).
1. Release the two spring tabs, at the outside bottom of the rear seat bottom cushion/frame by pushing them towards the doors.
2. Pull up on the lower front edge and disengage bottom. Remove CAREFULLY thru rear door.
3. There are THREE bolts (one in the middle sorta under the armrest) that are removed to loosen the rear seat BACK cushion/frame. Lift UP the seat back to disengage from metal slots by the parcel shelf. Remove, without scratching up anything.
EDIT: Just realized your wording was fine; my understanding was confused.....Nevermind