Details of the Bodine motor controller would be useful - their documentation should say what voltage range the speed-control pot uses - which will affect the choice of digital pot.
Another approach is to use a DAC to generate the voltage that would be at the wiper and replace the pot with a fixed resistor to fool the controller that it is still attached (motor controllers usually fail-safe if the control pot appears open circuit).
One Bodine controller (model 3910) I found docs for uses 12V on the speed pot (5V would be much handier, could even power the Arduino perhaps).