Another 273 commando build .. This one will be a "BEAST"

vibration might help the penetrant get into the crevices you need to break it loose. If you have a chunk of steel or brass, and an air chisel with an air control valve whip, you could spray the cylinder with whatever flavor penetrant you prefer(I like Mopar heater control solvent, myself), then starting with lower air pressure, use the air chisel to hammer on the scrap metal block on top of the piston(s).