This is a picture of my original 68 floor brackets. Studs straight up. I know 69 and 70 use diffent brackets on the floor but they still are straight up.
A closer picture showing the studs coming through the brackets. So what do these seat extenders do move the seat back to give you more leg room? If so I may want to look into a pair for my 68. Being 6'4 I don't have a lot of leg room in the nova.