A few years ago I seen a really neat frameless windshield in a 32 roadster. A fellow was able to find a Karmen Ghia rear window, free at a wrecking yard. He cleaned it up, flipped it over top to bottom, and laid out the profile line on the cowl of his fiberglass roadster.
He took his trusty sabre saw, and cut a slot about 5/16" wide all the way across the top of the cowl, so that the Karmen Ghia window would slide down into the slot.
He took a 36 grit grinding disk and roughed up the inside of the cowl a bit, set up some wooden blocks inside on the floor to keep the window from falling thru, and put some temporary restraints (wood slats and masking tape) on the top portion of window sticking up thru the cowl to hold it at the perfect angle. Then he mixed up a batch of resin and mat, and glassed a pocket all around the "buried" side of the window, and let it overlap about 3" all the way around the inside of the cowl.
When the resin had "kicked" he removed the blocks and props, and had one of the slickest roadster windshields I ever seen. The only problem I see with this, is, if that windshield ever broke, he would have to grind the entire pocket away under the cowl to replace it---However, it looked super trick, and was virtually free.