Spinning studs on barracuda grill, any tricks?

I believe it's just a small headed stud pressed in a thin flat to keep them from turning. If they are spinning and the grilles are still on the header panel, as others, I'd say you're doing some die grinding or rotary burr work. I think the grilles would need to be disassembled to replace any broke or cut off studs. Member partsmonsta could tell you for sure but I haven't seen any recent posts by him.
Extreme, but as a last resort option, maybe you could pull the heads through with a good set of vise-grips.