Don't use the rope-in method, it works for some cars but isn't easy or nessessary on A-bodies.
Get a couple of these install sticks, place the gasket in car first, then place the glass in the lower gasket channel and carefully work the glass into the remainder of the gasket with the sticks. use a little spit if you want to make it a little easier to draw the tools through the gasket/glass.
Use a small bead of windshield sealer on the gasket/pinchweld joint if you must, making sure you only seal the top and sides. leave the bottom alone, if water does get in there it needs a place to get out.
Method is the same for front and back.
http://www.ebay.com/itm/Windshield-..._Automotive_Tools&hash=item5647e9c22c&vxp=mtr