Spinning studs on barracuda grill, any tricks?

I’ve encountered this many times on 67-8 grilles. I’ve had some success with applying pressure by pulling against the stud while trying to loosen the Palnut, and if it’s still in the car, that may be the only way. If it’s out of the car, you may be able to slip the end of a small flathead screwdriver under the head of the stud to try to keep it from turning, or grind a small slot in the head of the stud and try to keep it from spinning with a flat blade screwdriver!