I was looking into that yesterday. my guess is that one stepper motor controls the secondary butterflies, this one won't do the job. The primary appears to have a stepper motor also but it has very limited stroke and is only for the idle position stopper.
I have been looking for a modutrol with enough torque to compensate for all of the spring resistance to govern the throttle bodies. The control circuit is already figured out and in the works.
I thought that since there is a wheel speed sensor.... The new HD's that are throttle by wire have a stepper motor that controls the throttle and cruise is easily incorporated.
Hook your secondary stepper motor to your primary throttle plates and remove your secondary throttle plates. That way you will have no control whatsoever over your motorcycle so hang on baby