The 67 Mustang has what's called a "sewn in" or bowstyle headliner (several panels sewn together) and is suspended with metal rods and then attached at the front or rear and pulled in the other direction to tighten it up. The correct way to install the headliner in the 1967 mustang is to remove the rubber that holds the glass and glue the headliner cloth to the metal lip that holds the "glass rubber" in it's place. This is the way it came from the factory; although it can be glued to the top around the back glass; and then tucked under the rubber that holds the glass in place. A high quality contact adhesive will hold the headliner in place for a long time like this; and some professionals do it like this. Something that is note worthy; most of the time the rubber seal on an old car like the 1967 Mustang have dried out, which makes tucking the headliner under the rubber quite a bit harder. Chunks of it may come off while tucking!