If I understand you then you are wanting to connect the bolts that are behind the seat. On mine it is all wood also. There are two big springs with plates and a floating bolt in the center that hold down the wood to the frame or wood block underneath to the frame(metal frame of course) Anyway this spring kind of holds down and also keeps the back of the truck sort of floating and keeps it from bouncing up as well. Maybe you can see these in your parts. Should be a whole in the frame to accept all this. Mine were very rusty and needed some furbishing to work. I haven't seen any for sale anywhere.