Swedefish: that canvas topped '64 Barracuda is known as the Landau, you can read about it here. Prototype.
http://www.enbcom.com/cuda/stuff/landau.html
Nobody has mentioned this rare option on a '69 Barracuda: There's a guy here in Ottawa with a '69 Barracuda with fold down rear seat delete and rear carpet delete. So he's got a fixed rear seat and black cardboard type material lining the rear cargo area. Very strange.