The original stereo is a dual-post style,because the two knobs, as opposed to the stereo I have(pic in my last post) which is a "DIN" style stereo. They both mount different, the dual-post has a small rectangular whole and two round holes for the volume knob and tuner knob, and the DIN style mounts in a larger rectangular hole. There are places that sell the "Dual-post" style stereo's that look original and are a direct replacement, but will also control a CD changer. truck has these. A headunit is the stereo, just another term for it.