I am resurrecting a 1970 JD 1020 3 cylinder gas tractor which has been sitting for about 20 years. It appears due to the amount of antifreeze in the oil that the head gasket has rotted away.
What am in for?
Billy, welcome to the MTF site!! Great place to get and share information!!
Head gaskets generally don't rot, they get weak during use and pressures blow out a part of them. Pull the plugs and see what they look like. Even after years of sitting they can often tell a story of the engine's health when it was last running. Then pull the head off and carefully inspect the block deck, the head gasket itself, and the surface of the head for any signs of blown out gasket or other damage. Coolant in the oil, if run very long that way, may also have scored or frozen up bearings.
Before you pull the head if you haven't already done so, pull the plugs and carefully rotate the engine by hand. You are looking for full, smooth rotation through 360 degrees with no stoppages or real tight spots. Take notes on how that goes.
Even better is lots of pics of the parts as found before you start cleaning them up for replacement and reassembly. Lots of clues can be had from just examining them.
Good luck and if you can, let us know how your project is going.