You have selected 30 inch 4 Leaf Slipper Spring 2000lb Capacity. If your old spring measurements don’t match up with what’s listed, You may have your trailer loaded, or the spring may be old and flattened out. It is not uncommon for leaf springs to measure longer than what the stock size is listed. If this is your issue, Measure the center of your spring hanger holes. This will give you a more accurate measurement.
Double your spring capacity to figure out what your axle is rated for.