Hi there, That 78 Gremlin would have the Audi powerplant unless somebody put some other engine in which I seriously doubt. As for the window, I doubt a glass shop whould actually make a window and then carefully put that little frame on. I'm sure there is somebody that would do it somewhere. Not that it is much help but that window is shared by the 79-82 Spirit sedan(which is virtually extinct) and the 81-82 Kammback(Ditto) as well as the 77 Gremlin of course. It wouldn't hurt for the person looking for the window to join an AMC club and put the word out that their looking for that rear hatch. Good luck Paul