Ok not a lot of options out there! let me ask you you guys this; the mechanic is telling me it cant be welded because its on the inside. could a qualified machine shop cut out a portion on the outside of the water jacket to get into it to weld, and then weld the water jacket cut out back in?
Did you look at some salvage yards. To have a machine shop do all that work is going to cost more than the tractor is worth and it could possibly break again.