Thought id share some tips and pictures of installing a headliner. I just did this on my 68 today (sedcond one ive done). hope this can help someone.
super weatherstrip adhesive (2 tubes MAX)
50-60 paper clips (clamp style)
get your headliner laid out and warmed up to get all the wrinkles out. also, transfer all the rods into their correct spot.
most likely the cloth channels will be two long. get the bows centered in these channels and then snip back the cloth about 1/2" past the 90* bend as shown
make sure to get about 50 or so clamp-style paper clips from any store with office supplies. they will be your many hands!
take the whole assembly into the car and starting with the rear, put the first bow in whichever holes they came out of. Then make sure the the cloth channel has no wrinkles in it by pulling even on both sides. Snap the bow into the clip. The clips may be very brittle and/hard so dont try anything 'creative' to get them in. Well, actually the way i did it was a little primitive; i layed on my back and pushed it in with my foot. Push on one side of the clip and it should 'open' itself up and feed the rest in. you may need two feet (perhaps a flexible friend/wife) to help get them in. this is probably the hardest part of the entire job! Perhaps new clips are easier but i just reused the originals.
Pull the headliner forward and back to see if there is enough material (just to be sure its the right one). pull the front really hard and lock it down with a few clips. then pull the back hard and secure with clamps. This should set all the bows/clips into their position.
Glueing: I used something different this time, its a little metal red tube of super weatherstrip adhesive (pictured in the next photo on the roof) Starting with the front, start in the middle (about 5" section) and pull it tight (and somewhat a little outwards. if you get wrinkles you can work them out when you get to the sides. But dont pulle TOO much to the sides, just enough to keep the wrinkles out of your 5" section. lay a bead of glue on the bottom side (or top OR both top and bottome depending on how much glue you have) of the flange and 'wrap' it around while keeping it tight. Once its wrapped around throw a few clips on it. Next pick a side and repeat the process then do the other side. dont worry about the a-pillar corners yet...
do the exact same process with the rear. its much easier with the windows out!
Here is a picture of the rear after i glued it down. there are visible wrinkles but they will come out when you get to the sides so dont think its screwed up.
Pick a side, any side. Repeat the glueing process by starting in the middle (where the two large clips are). after taking this picture i notices the seams were a bit loose so i just pulled a few clips and pulled a little bit and worked them out. This glue stays workable for quite a while but is not runny. good stuff
By this time, the front was dried so i took the clips off (becasue i needed them for the sides) and put the front trim on which is basically a BIG, long clip. also, this is when you work the corners into position. By now you understand how to work the material. I used a few screws to hold it tight then piled on the glue.