The middle piece you are missing is the floating bow (mid-49 on). This piece is bent like an "S", so top goes in then bottom, it does not attach to anything but the cardboard liners. It will look a bit like this when installed (early fixed bow example).
https://www.flickr.com/photos/advance-design_parts_co/18149693683/in/album-72157631867396207/The bow does not come with the liner kits, I am not sure if they are reproduced? Do you have the rear screw in bow as shown in the picture?
