If your tractor steers really hard you likely have the older steering gear and the lower bearings on the spindles are worn out. If you take the weight off of the front wheels with a jack do the spindles  drop down against the upper steering arm? If it moves a lot than you will most likely need new bearings. That will make it steer a lot easier. You might want to replace the spindle bushings at the same time. Have fun with your oliver.