Pulling the head would not be a bad idea and checking the valve train because you probably have stuck valves too. I've got several of these old motors to run after years of setting stuck and almost all of them had stuck valves witch will result in bent push rods. Some ran good most didn't, most of the time if you get the motor to turn over you'll find the rings stuck in the pistons bad valve seals and as big Rick pointed out rust in the cylinders. If the carb was open to the elements you've probably got a couple of cylinders full of water and what ever else happened to make a entrance. If you don't pull the head just keep adding the magic potion in the plug holes and gently try the pry bar to the fly wheel with the plugs out. If or when it turns over it might be a good idea to remove the oil pan and clean out 50 years of colected sludge and filth so the oil pump might have a chance.
