Not sure of the hydraulics available on that tractor but if mine did not already have power steering I would probably try to retrofit the steering assembly that is on some 1960-70 Ford cars such as what is on my 1971 Torino. It has a separate valve assembly and cylinder.
Also if you do not have a separate counter weight on he rear of the tractor, that in itself will make it a bear to steer. Weighted rear tires do not take weight off of the front tires.