Just to be the contrarian and *again* ask the old question ... Why do you (OP) feel the need to "upgrade" to power steering? I ask this because we've had a lot of people come through the site over the years thinking they had to go the P/S route for "better" steering ... When all they really needed was to be more informed to make a better decision. Sometimes, P/S is the better route. But not always.
In my opinion, after completing two frame offs, and spending a fair amount of time behind the wheel of a '65 GMC 1.5 ton with less than 10,000 miles on it (firetruck...
), it is my experience that an original front axle set up, refurbished to factory specs and adjusted properly with good, properly inflated and balanced tires, gives 95 percent of the same feel and control of a power steering set up without the hassle and expense of cobbling it all together.
And in the case of my unrestored/*mostly* original '49 one-ton, it steers about 80 percent as well as a p/s set up. The firetruck, at max gross weight of 19,000 lbs, steered with one finger at any speed other than a complete stop. And even at that, it wasn't bad. On the down side, out in the field or on rough terrain or negotiating deep ruts ... the wheel could be ripped out of your hands. Got whanged in the funny bone by the Brodie knob that way once ... Still wouldn't want to upgrade to power steering, though.
I had factory PS on my '72 GMC 9500 road tractor, though -- and was glad for it.
On a light truck, I think a well-maintained original (non Pwr) steering is as good for most scenarios.
Just food for thought.