since i didn't remove the old headliner myself i have no idea in which holes i have to install headliner bows, maybe some one here installed him/herself a new headliner and can remember the holes used with a 66 fastback , i guess it is for every 66 fastback the same?

i tried with using the old headliner if i could find out what holes were used and i think that for the rear bow it was the rear hole.
at least after installing the retainers and trying to fold the edge around rear window edge i got the impression that if i used the front (1) hole the edge on the rear of headliner would be a little short to fold around the rear window edge

for the other 2 bows i have no idea... tried all but couldn't make a good guess.. but if i had to guess anyway.. i would would guess for both bows the 2 front holes

any help appreciated
thank you

 

I have a 69 fastback that I installed a headliner, but I had the benefit of removing the old. Can you not simply test-fit the bows in the holds?

Perhaps you could visit with an upholstery shop and get some help.