I can help you with the Top Exterior Windshield Molding. There are Studs with Nuts that you must get at from the inside of the car. The rest of the Moldings are all held on by screws. If you are not going to save the rubber, what I do is just cut it off with a utility knife. I just cut the rubber along the edge of the Windshield to free it up, then just carefully remove it. I only cut the top and the sides. It will then just lift out of the bottom with no problem.
Haven't lost one yet, lol.
You will also need to remove the Cowl Vent Grille to get at the screws that hold on the 2 bottom Moldings.
-Parting Out over 75 '58 to '73 Full Size Chevy Cars-
-National Impala Association
-Vintage Chevrolet Club of America