Drive by wire and having an actuator for the cruise control are not one in the same. The drive by wire consists of a stepper motor attached directly to the throttle body, with accelerator position sensors on the pedal and another in the motor itself. The 2 sensors in the pedal work opposite of each other as a redundancy check. My 04 GTO had the same throttle body as an f-body, when the GTO went LS2 in 05-06 it had the DBW system. If you want to use a cruise actuator as a throttle motor, I wish you luck with that
If you're looking into a DBW system, start doing your homework on what it will really take to get it done.