When I was redoing my 69 cuda plastic grills I used a JB weld epoxy. Worked great, sandable.
Side note, in your last pic, chk the metal tab that holds lens in. Looks like plastic is missing that holds it firm.
I like JB Weld. I found recently Devcon Epoxy works awesome as well. It's one of my favorites now. The dark gray works great. They have one that dries cream color as well. Devcon Plastic Steel Epoxy, 25ml
