On a 73 chevelle, Would anyone know if the 4 top dash screws (2 driver side screws, 2 pass side) that go in at an angle on the defrost vents, Do they screw into the plastic duct work for the defrost vents, or do they screw through the dash into the cowl area? My defrost duct work is not up tight against the defrost vents on the dash. I'm thinking maybe the screws go though the duct work to draw it up tight? Does anyone have the duct work out? Maybe take a look and see if there are screw holes where it meets the dash. I'm getting the windshield replaced again and would like to get it straightened out. Those screws are a pain with the glass in. Thanks for any help..