Look for a 1/2 ton Dodge pickup axle about the same year as your Cat. These axles were used for quite a few years, but come in a variety of lengths and spine counts. The passenger cars used them too.Measure the length and spline count. If it broke under the tapered end flange you will need to get one of them too. Make sure the axle extension fits the new hub if needed. Some may need machining. Check out the condition of the key as well. You will need to press the drive hub off the tapered shaft to replace the tapered roller bearing. You need to find a wrecking yard that has nothing but old Chrysler vehicles.