In my '73 there are 4 bolts holding the seat down at each corner of the frame....3 you can remove from the inside of the car, and 1 is done thru access holes in the frame from under the car.
the rear outer botl is the frame bolt. it helps to remove the tops when its time to life them out. I hope this helps on your '69.
(im sure to be corrected at this point, Eh?

)
Another SE Michigan vette....welcome
~Chas
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"When the sheep's see the wolf packs up-close, they cry for help...but when the wolf pack hides in the shadows, the sheep seem to forget that they could end-up as kill and venture into the forest edge...."