I just looked at all this on mine last night, getting prepared for the day I put the doors back together. The kit that I have provides the channel piece that you are talking about and it definitely will need to be riveted to the divider along with the short vertical vent strip on the other side. Some other details that I went through is a sealing rubber that is retained by a flange on the inner lip of the outer door surface and an anti rattle strip the is attached to the bolt on trim.
