1 Our friend Mike Ambrose at Ambrose Custom Interiors knows his way around automotive interiors. He removes the rear window by carefully prying the window trim up and away from the car and rear window. | 
2 Continue removing the window trim along the bottom of the rear window. This windshield-clip removal tool separates the trim from the clips underneath. |
3 Once the trim is removed, cut away the top side of the rubber seal with a razor blade to separate the glass from the body. The seal is hard and dried out, but with enough pressure, the blade will cut through it. | 
4 Continue to cut the rubber seal along the side of the rear window. |
5 Using a plastic molding-removal tool (aka bone) to get underneath the glass, separate the glass from the car. After one or two of these are placed under the glass, the tool is used to lift the glass up and away from the car. | 
6 Once the glass is separated from the car, two people can easily lift it up and off the car. We're surprised at the thickness and weight of the car's factory glass. It's also scratched pretty badly, but at more than $500 for a new one, we'll reuse it on our daily-driver project car. |
7 With the glass out, remove the inside portion of the rubber seal from the car, revealing whatever rust damage is under the rear window. As the next photo shows, the prognosis was less than ideal, but it could have been worse. | 
8 After blowing all the dust and accumulated debris from the window channel, we found a rusty hole in the lower driver-side corner of the window channel. This is a major turning point for us, but each car and circumstance will be different. We don't have time to take the car to a body shop for proper repair, and since our car is a daily driver, it's not a huge problem. Ideally, the rust should be cut out and replaced with new metal at a body shop, but some extra urethane sealant will have to do for now. |
9 Luckily, the situation on the passenger-side is better. There could've been holes on both sides, and although there is some minor surface rust here, it's something we can live with. | 
10 With the rear window out, it's the perfect time to consider headliner replacement unless the existing one is in excellent condition. Remove all items on the roof, including the sunvisors, coat hooks, windlace, inside windshield trim, and shoulder belts if your car has them. During removal, note which roof holes the headliner bows are in. In most cars, there are two sets of holes for each bow. |
11 At only $28.95, a new headliner is a cheap appearance upgrade if you're going so far as to R&R rear-window glass for a leak repair. They are available from National Parts Depot in Moonskin for '65-'70 Mustangs and Tier grain for '71-'73s. | 
12 Be sure all four bows go in the same location as with the old headliner. Lay the headliners side-by-side, and slide the bows one at a time out of the old headliner and directly into the new one. |