Industrial expert's opinion is maximum torque required to actuate ball valve is
"Torque ability to open under large differential pressure and to close under high flow conditions "valve manufacturers give guaranteed maximum torque values at these pressures, hence they are taking many "internal" calcs into consideration, such as surface finish tolerance, dimensional tolerance and once they come up with a global sum of factors that can have effects on valve rotary motion...they slap on a extra 15% to 30% to these figures, to be on safe side.
With a small rack & pignion actuator, you wont be saving much (if anything) on single or double acting by shaving off a couple of Lb-in...not for this size valve/actuator assemlby. I could understand for instance if you were doing all this for anything above 3" #300 where torques start to have adverse effects on actuation pricing and overall dimensions(change fron rack to yoke types).

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