Buying a used motor without it running can be a real danger. I would proceed with caution. You real need to bench run the motor. To install it without a stand test is a big gamble. When we sell them we mount the motors on stands, hook up the panel introduce a source of cooling water, usually a hose just feeding into the raw water pump. If this cannot be done minimally a compression test, which require injector removal.
Do you have any history on the motor? Why was it removed with only 700 hours with the gear? If none of this can be done then at least bar the motor over to make sure it is not seized. Also carefully examine all fluids. Make sure the gear oil is free of water and clear.
Examine the coolant it should be nice and reddish pink in color with no brown traces. It is always good to drain a little coolant from a low spot on the motor. Motor oil also free of any coolant. Removing the valve cover also is a good idea when you bar the motor over.
Examine the paint carefully for touch-ups that might hide brownish paint from an overheat. Also pull the end cap off the heat exchanger and give that a good look. Stick your finger in the turbo and see if the vanes spin freely.
Lastly if you can I would consider pulling off the head. With that removed and a hand spin most of the major components can be looked at.
In closing if this is beyond what you feel you can do, pay a Cummins Merchanic to look the motor over as best he can. Still a gamble
