Ken, the liners you refer to are different for FE to FC. They are well made however, they become very brittle with age.
I suggest you make new covers out of plastic and use 3M spray on adhesive, this should work provided you wipe the doors down with Prepsol before spraying.
I will shortly post some photos of these early liners - sometimes if you have an original rust free car its just as well to leave it alone and keep it dry.
Having said all that, I have to have new door cards made for my very early blue FE. A look inside the front doors reveals, red lead (or something) half way up the frames, but NO paint whatsoever above this. No wonder they rusted so quickly
Regards
John