68 Barracuda fastback rear window moulding question..

So I am trying to figure out how the piece of interior trim, the curved piece that goes directly under the rear window, attaches. Its like its supposed to screw into air, and I don't think that's what Mopar intended. Does it take some sort of spacer to make it to the rear window channel? I am almost ready to install the back window, which I hear is a pain, but need this in place first. Any good tips or tricks to make the rear window install go smooth would be awesome as well..
Thanks !
Dave in Colorado

there are small plastic spacers that attach there , I cant find any pics of mine.... they fit between the trim and body

Here is a shot from underneath

Picture of the side

Here is the left rear corner

Right corner/middle

Close up of retainer nut

As far as installing it, I would start at the bottom of the window setting that into the seal, that is already installed on the body. Then work the window up the sides both left and right towards the top of the glass and finish with flipping the top part of the seal over the glass last. When I removed mine I started with the upper corners, worked a little down the sail and across the roof, working side to side. Finishing at the bottom, don't forget to use some bedding/glazing material in the weatherstrip to seal the rubber to the glass, go slow and use nylon sticks to help work the glass into the seal.

Awesome, pics help a lot. Now where do I find those spacers? Time to start the search... Thank you so much!
Dsve