Close off he ports by bolting on a heavy well sealed steel plate. The bypass ports are a problem. Since iron is tougher than epoxy, you might use epoxy to get a good seal. Then make an adaptor to screw into the spark plug hole and screw a grease fitting into it. Fill the cylinder with penetrating oil followed with high pressure grease. A grease gun can develop over a thousand pounds of pressure. Depending on how rusty the iron is, you might re-enforce the cylinder with a row of Aircraft style hose clamps. A little heat around the base of the cylinder shouldn’t hurt.
