[njsteve]

I ended up repairing the broken section of grill. I first filed the edges so it was a clean area. I then hunted around the house and finally found an old broken plastic wiring harness retainer from, of all things, my old long-gone 1971 Hemicuda Convertible! (So now there's some Mopar donor material in this Pontiac...) It was made of the same type of heavy plastic as the grill and almost the exact same age, give or take six months.

I cut a small section off and filed it to the correct width but left it with an extra amount of material 3/8" long so I could handle more easily while fitting it into the grill space. I also pre-scored a line before the 3/8" tab so I could break it off once it was glued in and set.