M5 steel rod. Looking at mine, I cant get at the hinges because some git layered filler on an accident and corrosion damaged panel so the hinge pins are half inside the filler. The screws to the body dont come undone either. Well chewed. So its a new panel , cut the old one off, recover the hinges or replace them.
You'll get them out of the body by building weld on the screw heads. The heat cracks the rust and they unscrew with your fingers. Never failed, done it LOADS with these particular screws. You won't even damage the paint as the hinge will soak up the heat.
I shall give it a try but there is well buried frilly steel around, and the screws point in at about 20 degrees to the horizontal, and the seal channel is long gone.