My hood vents leak like crazy like most 67 coupes. I looked at covers that screwed on and none of them seemed to fit right, or stay on at freeway speeds, so I bought some vinyl sheets used for bumper stickers and cut out my own. I cleaned the vent area really good, plus heated up the area with a blow dryer and then heated the vinyl. it won't last forever but it weather really well plus my order came with enough to replace it as needed. I recommend it. heres the link to the vinyl I used off amazon.
12" X 24" 6 Sheets of Matte Black Permanent Adhesive-Backed Vinyl for Craft Cutters, Punches and Vinyl Sign Cutters ? Vinyl Ease V0153
12" X 24" 6 Sheets of Matte Black Permanent Adhesive-Backed Vinyl for Craft Cutters, Punches and Vinyl Sign Cutters ? Vinyl Ease V0153