1969 Rear Seat Detail

I have just purchased my first Mustang...a 1969 Fastback.  I am going to have the rear seats upholstered to match the front custom seats...the car does not have the "fold down seat" option, but the seat will fold down giving you access to the trunk.  The car does have a package tray.  My question is...what is the rear seat detail for a car with this seat configuration?  It appears that the back of the rear seat should be bolted to brackets in the trunk.  Also, there is metal trim around the outer edge of the rear seat backing (wood) and the upholstery does not extend all the way to the edge of the metal trim.  Should it?  The way it currently sits there is a gap between the edge of the seat trim (metal edge) and the rear interior quarter trim.  To my untrained eye it looks like I need to build a whole new seatback that actually fits the dimensions in order to eliminate any gaps.  Also, is there another piece of trim between the seat back and the trunk?  

I apologize for my ignorance, but would appreciate any help.