this is what i was talking about; however, it's now primarily used for trucks running huge tires, but it was a factory option on 4x4 trucks of our era instead of power gear boxes (where now days it would be used in addition to them) while it wasn't offered in 2wds, it would not be hard to retro fit something like that onto a beam truck... it would basically follow the same idea as putting steering stabilizers on a 2wd truck, but the mounting areas would need to be much stronger than clamps. that would be the down side is it would take some fab work to make it work... the benefit is you don't mess with your current steering gear or column. I think you'll end up having to mess with both even if you get a bendix power steering gear as it had a shorter column (although not as short as the newer PS columns.

 

Not the same thing as the modern equivalent.
The original power assist was indeed a ram, but it was integral to the dedicated linkage ends and was a small diameter, weak-ish and heavily leak-prone system.
Probably not weak for a 2wd with normal tires, so that's not a big downside here. But the leakishness is a big detractor.
Never heard too many complaints on how they worked, when new. But everyone that has one usually ends up with a very oily undercarriage and garage floor, until they rebuild the system. Again and again...

Maybe, maybe not...
As you said, some fab work required. But if you mean the original system, then you're probably correct since the hydraulic assist was based on the input of the physical linkage from the steering box. So a manual box is fine if you can orient the ram and linkage accordingly. Seems seriously custom to me though...
But if you mean a modern ram-assist setup, there are still some serious modifications to your existing power steering box to tap into the hydraulic innards to control the external ram. A full ram steering setup would not be very desirable for the street, and they also require a special pump integrated into the steering column shaft. But if using an existing power steering setup, you just have to have someone modify the box.
If you are starting with manual steering (is that what you have?) then you'll either need that special box (I forget what they're called) or an original linkage based ram-assist setup, like you were referring to.
But with one of those, wouldn't you need an entirely custom linkage setup? The 4wd trucks were quite a bit different, linkage-wise, as you noted. And I think that means that they are far enough off that you would not be able to customize the existing linkage to work, but would instead have to create new link bars from scratch.
I think? Unless someone has a kit...

Paul