67 Barracuda Grill restoration Help

Recently? I'll have to give him a shot...

Thanks!
Working on my 67 grille and the carriage style bolts are 8-32. Maybe the size 10 would work but dough if the square is the right size. the stock ones are around .180 on the square. Standard 8-32 carriage bolts have a smaller square than the ones on the grill.
I like the idea of using a flat head screw and welding the head to the mount.
I'm trying to find an earlier discussion on what type of rivets to use.
I looked at Eastwoods solid rivet kit but the pneumatic gun looks like it would be way to big.
The earlier forum talked about the rivets that someone had use.
Anyone have and ideas. Pop rivets would work, but I'd like to stay with solid one.