Bolens used (on the large frames) what I prefer to call "power assist steering". There is no steering control valve or orbital valve used. Instead, there is still a mechanical linkage between the steering wheel and the tires (if the valve bottoms out you can still mechanically steer the front tires). The valve provides the power assist by opening when the steering rod trys to push the assist cylinder. Oil is sent to the cylinder making the cylinder "keep up" with the steering rod. Some early cars (ford falcon/mustang) and farm tractors also used this type of steering.
The other type of power steering used on modern equipment is what I call "hydrostatic steering". This is where there is a steering control valve or orbotal valve attached to the steering wheel and a hydraulic cylinder attached to the wheels. There is no mechanical linkage between the steering wheel and the tires, only hydraulic fluid.
Also note, to install the Bolens factory large frame power steering unit you need to plumb it "in series" with the spool valve. You cannot just use two tees and plumb it in parallel. Oil from the aux pump on the hydro needs to go to the steering assist unit first, flow through the steering unit then go to the spool valve as it normally would.