I have used PB Blaster as a penetrating oil for rust, instead of the WD-40. Those should be pretty easy to get at and need to be replaced any way, so I would suggest putting on some goggles and using a hammer and chisel to dig into the head of the bolt to turn it. A few good hits and they should loosen up, so that you could finish taking them out with the vise grips.
Good Luck,
Bill M