Removing bolts on fenders

[72ChevyAZ]

I have started to disasemble the rear end of my truck. Every bolt I turn to try to take off just spins and obviously the top of the bolt is smooth. Soooo........What is the best way to remove these old stubborn bolts? Grind off the head? Make a cut in the top so a screwdriver can fit? This is my first time removing panels. I need all the help I can get!!

[Evans]

Just tackled the same thing with mine when pulling apart the front clip , I ground the heads off ....