[68-69-70Nova SSL78]

I'm restoring a 1969 L78 Nova turbo 400. My question is did the turbo 400 L78's come with 4 or 5 rear leaf springs? Mine has 4 now but want to make sure. I believe Camaro's would have the same setup. Does anyone know why 4 or 5 leaf springs were offered? Was one or the other considered more heavy duty? Any info would really help. Thanks