I just finished installing my 76 wagon windshield for the 2nd time in 2 months.
First time I used the rope method. I did not use the foam tape at the bottom of the windshield gasket. I did not put sealant in the gasket groove that goes over the pinch weld because I didn't want to drag it into the the car with the rope. I did apply the sealant all around the outside of the gasket and between the glass and gasket. Because the pinch weld along the base of the windshield is so uneven, the water was able to find its way up and over the pinch weld.
The second installation, I placed the gasket on the pinch weld. Taped the gasket to hold it up along the top. Pulled the gasket off of the pinch weld a little bit at a time, applying CRL 7711(cartridge) into the gasket groove and placing it back over the pinch weld. I made sure plenty was installed along the bottom and the two lower 90 degree corners. I then continued up along both sides and across the top, a little bit at a time. Using masking tape along the top really helps keep the gasket up once the sealant is applied.
Set the glass down into the gasket starting with one corner. Pull up the outer lip of the gasket using a flat plastic tool. Pull the tool across to the opposite corner, seating the glass as you go. Be gentle and patient as you pull the lip up and around the other bottom corner. Now the glass will lay there. Start up one side, pulling up the lip as you go. My helper used another plastic tool (from the inside)to gently push the outer lip out towards me so I could hook it and keep sliding my tool up as we went. Go to the opposite side of the car and do the same thing. Finally, work your way across the top. Remember to pull out the masking tape as you go.
I used a brand new gasket from Steele Rubber. I did the installation out in the sun. The heat seemed to make the gasket more pliable.
Next I used CRL 1716 sealant. It comes in a can and is flowable. I purchased the suggested trigger pump that screws onto the can. Start at the center top of the glass and pull back the gasket lip and insert the metal tip of the pump. Apply sealant at the back edge of the glass and enough extra so that it oozes out as you let the lip back down and pull the tip along. Avoid nicking the edge of the glass with the pump tip. Apply sealant along the top. Next start at the center of the base of the windshield and pull out to each side. Finally, apply sealant to both sides. Apply tape on the body at each nail head, screw hole and drain hole and mark with a pen. Install your trim clips on the nail heads and apply the 7711 (cartridge) sealant around the entire outside of gasket, make sure you get it in and around the clips. Clean out sealant from the six drain holes along the base of the windshield. These holes drain into the area under the cowl vent. Screw in the six metal plates that hold the gasket down tight against the base of the windshield and keep the glass from shifting down. Install trim at base of windshield, remember the screw in each corner. Install remaining trim. Scrape off the majority of the sealant that has oozed out onto the glass. I used mineral spirits for clean up.
I read somewhere that spraying foaming window cleaner on the glass helps with the scraping. I did not try that though.
The plastic trim tools were purchased at Harbor Freight. The sealant and trigger pump were purchased from a C.R. Laurence distributor.
Sorry this was so long.