Keep in mind that the production year can vary from the model year. In this case the model year is 1958 as the 601 series began with model year 1958 although production started in 1957. The model year is the one used when looking for parts. Below is a page from the Ford 4 Cylinder Tractor 1953/64 Parts List. Note that Model 601 tractors have a year range of 1958 - 1962.