Hi everyone, I have a 91 firebird and I'm attempting to mount my aftermarket fenders on the car but I'm struggling to find the correct size/thread pitch of bolt for the lower back (and threaded) hole, as pictured. I googled it and was told the correct size was m8x1.25, I've tried that and 1.00 thread pitch but only get about four or five turns in before the bolt locks up. What do you guys recommend?