The OEM linkage booster system has multiple hoses and leak points.  Also you have to move the stud on the control valve in order to gain power assist.  The valve is downstream from the steering gear (between the linkage and the pitman arm.)  This fact means that any movement of the stud is magnified by the gear box ratio (16:1 in the case of the Corvette manual gear) and will translate to lost motion.  

 

An integral power gear or a rack and pinion gear has the valve on the upstream (steering column) end of the gear.  So the action of the rotary valve is a direct relationship to the input from the steering wheel.  This fact should weigh toward this type of steering system.  

 

Saginaw engineering tried to talk Chevrolet engineering into a Corvette integral power gear upgrade back around 1967-1968.  They actually engineered a special cast housing that would bolt into a C3 chassis.  The C2/C3 frame (in the gear mounting area) is not parallel to the centerline of the car.  So the mounting pads on the gear had to be shifted by roughly 4 degrees in order to match the frame.  Also the front crossmember had to be modified to clear the forward part of the power gear.  A 1968 Chevrolet Engineering Corvette was modified to accept the prototype Saginaw gear.  Chevrolet's evaluation indicated that the integral power gear was not a substantial improvement over the OEM linkage booster system. 

 

Modifying the production front crossmember is quite an expensive change.  Whether the Chevrolet decision was more money related than actual performance, we will never know. 

 

I do know this, one of the prototype gears managed to escape from Saginaw engineering.  There is a 427, 435 horse, 1968 convertible that still has an integral power gear (and a T&T steering column).  The only one in the world. 

 

Jim