steering box replacement recommendations

[kxnomore]

It was bad enough that my truck had very loose steering, but now it's leaking power steering fluid all over the place. Both the Pitman arm seal and the input shaft seal are leaking 24-7.

Anyone have any tips on the best steering box for our trucks? Stock, or maybe one from a later year?

It's a 71 K20 by the way.

Thanks in advance for any suggestions!!