I fully agree with Mick that the electric steering assist is the future. However, it is just that, an assist. You still use the original steering box and related components. I have seen many worn out steering boxes on these 60+ year old trucks. In many cases someone is looking to upgrade to PS because the box, drag link, and pitman arm are worn out. They may also want to make a change because it steers like an old truck. Look at the overall condition of all steering components before changing anything.
Fred