On the car - you could apply penetrant and withdraw the castellated nut a couple of turns, heat the ends of the arms with a propane torch (avoid heating the pin itself), then use a large c-clamp with a socket wrench around the head of the pin (that would allow it to move). Tighten the c-clamp and push the pin out.
Off the car - you could remove the kingpin castellated nut and the shock fixing bolts; and take the shock with upper trunion to the work bench.
Apply penetrant such as kroil or PB Blaster to where the pin goes through the shock arms. Undo the castellated nut on the pin and replace it with a regular nut; back the nut out a couple of turns but leave it on the pin. Turn the shock sideways and support the arm ends over the gap in a large vise. Take your lead hammer and hit the nut - this should loosen the pin. Or if your vise is big enough you could use a socket per method one and squeeze the pin loose.