Here's some instructions I saved from an email a long time ago. Not my instructions, they're from another Moparite named Bill.
>That reminds me... has anyone successfully removed a windshield _without_ >destroying the gasket? I know the "proper" way is to slice the gasket away
>first, so that the glass can be gently pushed out of the channel with less
>risk of cracking.
Sure, done it many times. Firstly, obtain at least one nylon "glass stick" from a local auto glass shop. This is a nylon stick, about the size of a construction pencil, with each end tapered. One of the local shops gives me their old ones when I stop in and ask for a couple, and I use Brakeleen to get the old sealer off them.
Then, on to the job. Remove the lock strip or remove the trim and open up the locking parts of the gasket, depending on the year involved. This will be your first use of the glass stick, makes quicker work of the lock strip. Next, run the glass stick all around both the inside and outside of the gasket, breaking it loose from any sealer and breaking it loose from the glass. Be sure and work the stick down all the way into the gasket to the very edge of the glass, all around and inside and outside the car. The corners are the hardest. This will be much more difficult if someone has slopped some silicone seal or other makeshift sealer in there trying to stop a leak, but it is imperative that the strip be broken away at every point from the glass. Next, climb into the back seat with a pair of running or tennis shoes on and eye protection. Lie backwards in the middle of the seat (or with a Barracuda fastback, fold down the seat back and lie on top of that), and put your feet up onto the glass. Began pushing at the upper outer corners, working your way into the upper center of the glass.
This of course is a very delicate part of the operation, and you'll have to play it by feel and by ear to know you are breaking the upper edge of the glass away from the gasket. The glass has a bit more flexibility than you might think, but you must gradually break loose the entire upper edge and upper corners more or less together to do this successfully. Once the upper edge and corners are just beginning to break free of the gasket, add the side edges to your footwork, beginning to break them free also. At some point things will suddenly get easier, and you'll know the upper edge, upper corners, and most of the sides have broken free. Now gently push the upper
part further up and the whole piece will be free except for the bottom edge.
Get back out of the car, lift the glass up (with a partner on the other side of the car this is easier and safer) and lift the bottom edge on out of the bottom of the gasket.
This whole job needs to be done carefully, slowly, etc. You'll develope a bit of a touch or feel for how much pressure to apply, but its better to be conservative. I've removed quite a few windshields and back glasses using this method over the last 20 years or so. I've broken one windshield and no back glasses, due no doubt partly to luck but also to taking it very slowly and carefully, and thoroughly breaking the glass free of the gasket before ever starting to push it out.
By the way, this is the same way I put them back in also, just reversing the process and using two glass sticks and WD40 as a lube to work the glass back into the gasket. When you reach the magic moment so to speak, that top edge and corners will just pop down into place and you are done. I tried the "rope" method once and it didn't work for me, so I gave that up.
Also, one time I needed both glasses removed from a '69 fastback, and "thought" I didn't have time to get it done myself, so I contracted with a mobile glass shop to remove them while I was at work. I was totally shocked and pissed off to find that the guy charged me $40 EACH to CUT THEM OUT!! You can cut a glass out in about 10 minutes using a utility knife, heck if I'd wanted them cut out I would have done that already.
