My 280S has a bad steering box. When the pump is running, the steering box turns hard right and will not center.

I have located 3 used boxes. I would like to test all these boxes before replacing the bad in-vehicle one.

I would like to know if I could test the used steering boxes by hooking up a spare ps pump to one of my used boxes. Using a one hp electric motor to run the spare pump, could this arrangement test the used steering box prior to installation?

Or if anyone has a better idea, I would love to hear it.....

__________________
71 220D 169K wrecked
83 240D 118K sweet 4 speed
91 350SDL (one of the 60% good engines) 156K
84 300d (loaner to my sister) 189K
79 300SD (partswagen)
86 420SEL partswagen
70 220d (partswagen)
68 280s GASSER!!! under construction now
85 300sd 310K miles winter beater car retired
93 300d 2.5 turbo 168K wife's car
83 280SL euro 5 speed 155K
69 250S newest project 54K