These bolts are hardened and quite strong. If you take the time to remove the paint and other crap from the clutch head hole in the bolt head and use the correct tool in good shape the bolt will most times come out. 90% of these in my truck were threaded into sheet metal and came out easily. Those threaded into thicker material all came out with a little heat. If you do brake one, they are a little tough on the drill to remove.
Chevs of the '40's has them
