The best one I ever saw some 40 years ago was a hydraulic torque amplifier unit mounted under the dash.
It was on beefy homemade brackets, and the stock steering shaft was customized to fit. They used the stock steering box.
I didn't get to see the pump/reservoir, but that would be academic anyway.
The thing looked more-or-less cylindrical, about 6" diameter, 6 or 7" long, shafts out each end. Pretty neat job.
In later years, I saw the same tech used in bigger dunebuggies in the Yuma dunes.
PoW