Hi Per Arne Harefallet @perarnechonica-no
Alan’s correct, the only car that had factory fitted rear seats was Princess Diana’s. Her car though was always fitted with the rear Hardtop rather than the fold down hood – possibly as there was concern that someone in the back of the car might stand up and could injure themselves on the Targa Top’s T-bar if the car suddenly stopped.
Many owners wanted 4 seats, so many of the dealerships were happy to supply a Cabriolet with seats fitted from a Coupe – with the deal arranging to have the rear locker box out taken out and rear seats fitted. All the mouonting points were present in the car for rear seats and seat belts, as the Cabriolets were converted from near complete Coupes when they were built.
If you look around, you will see ltos of different rear seat arrangments in different Cabriolets – this is I think due to the dealer fitting whatever Coupe Seats they could obtain.