Jim Shea
For a C2/C3 power steering system that really didn't change through the years, the power steering pump high flows and low flows did change. The maximum pressure remained the same at 950 psi for all the years. Here are the flows:
1967-69 1.25 gpm @ 465 rpm 1.75 gpm @ 1500 rpm
1970-73 1.32 gpm @ 465 rpm 1.60 gpm @ 1500 rpm
1974 1.32 gpm @ 465 rpm 2.90 gpm @ 1500 rpm
1975-79 1.32 gpm @ 465 rpm 2.90 gpm @ 1500 rpm
1980 1.32 gpm @ 465 rpm 2.90 gpm @ 1500 rpm
1981 0.60 gpm @ 465 rpm 2.90 gpm @ 1500 rpm
1982 0.60 gpm @ 465 rpm 1.90 gpm @ 1500 rpm
The high flows (@ 1500 rpm) are strictly a function of the discharge fitting. Change the fitting, change the flow. The high flow rates might make your steering feel somewhat lighter.
The low flows (@ 465 rpm) are a function of the cam displacement inside the pump. The pump displacement was greatly reduced in 1981-82 in order to promote better fuel economy. The less oil that is displaced every time the pump rotates the less energy the pump consumes. I don't know if low flow rates at low engine rpms might affect hydroboost braking systems.
For you road racers that continually see high engine rpms, a low displacement pump will reduce your steering temperatures. Any Chrysler minivan built before 2000 will have a Saginaw P-pump with a low displacement 60 series cam ring inside the pump.
The 1974 through 1980 pumps ought to have plenty of flow.
I will try and determine if there is a range of service discharge fittings that will provide from 1.9 to 2.9 gallons per minute (or more).
I will also try and determine if there are service cam rings that will provide higher and lower pump flows at low engine speeds.