Check out the other headliner thread going on at
http://www.zr1.net/forum/showthread.php?t=18176
I used 3M Trim Adhesive and even with the FL heat the new cork base and fabric I used are sticking nicely together and to the roof so far.
I went with a cork base instead of the fiberglass pad because there was too much old glue on the pad and I was concerned the new adhesive wouldn't stick properly (and I figured removing it would be a PITA). I did use the pad as a template for cutting the material and the cork, and I stored it for later use if needed.
John