'69 Cuda rear seat

I'm presently working on a'69 Cuda Fastback for a guy that bought it totally disassembled.He bought it with the seats already reupholstered,I'm just putting the interior in it now and I notice the rear seat cushion is about 9inches shorter than the width between the inner 1/4 panels.I am wondering if this is the correct seat bottom.It looks funny with a 4 1/2" gap on each side,if it is correct is there something that is supposed to fill the gap.If someone could post a picture of this I would appreciate this.
Thanks