I can tell you a product sold at NAPA worked for me to fix the cracked filler inlet on my radiator. Its a two part epoxy with fiberglass matt, looks like it might be JB Weld epoxy but it is strong and so far it has held up. You will need some cylindrical "rasps" mounted to a drill and some medium grit sandpaper to contour the surface, otherwise its a piece of cake. Steve