I have installed (with help) headliners in two 64's in the past 8 years-the last one last year. They are diffficult, and in both cases we had to add material to fill in around the rear glass and down on each side of the rear glass to the hat shelf. There are some tack strips that usually have to be repared or replaced-especially around the doors where the windlace is attached. These tack strips can be made out of the panel board (not wood) that goes under the upholstery on the doors.Waterproof panel board is available in 36X48 sheets from "Perfect Fit" upholstery supplies. I used 7 sheets (about $8 each) and it made the kick panels, door panels, rear side panels,2 panels under the fromt of the rear seat, the one behind the rear seat back, and one panel on each side of the trunk. The trim piece that covers the tack strip at the back of the doors can also be cut from the panel board, but has to be covered with some type of material. I made these trim pieces out of 1/8" aluminum and painted them gloss black.
Be SURE to the wiring that goes front to rear before installing the headliner to be certain it is in good condition.
If you need more information, feel free to E-mail or call. Skeet