Rusted fresh air vent mount on 66 Cuda

use some Por-15 and some fiberglass matting. I repaired one with the same method. Take a wire brush and knock the loose stuff off then paint ^this area with the por and cut the matting to size,apply the matting to the por area,let it tack up then apply por over the matting intil your happy. The second part is messy as hell,buy one of those wide foam paint brushes,get some rubber gloves and a long sleeve shirt you don't care about and use some tape to fill in between the gloves and the shirt,dip the foam brush into the por,reach into the opening and fold the brush over the edge and coat the back side all the way around. If you have one of those swivel reach mirrors it will help you see back there to make sure you have enough coverage. This is a simple,cheap and quick fix and should last for many years