Have you consider rear camera? They are pretty cheap and minimum effort to install if you do it like how I did my 2 months ago.
Basically I brought a rear camera (integrated into the rear number plate light casing/holder) from EBay, and a separate 4.3 inch LCD display which I placed in an odd location (which works well for me). Basically I placed it behind my passenger seat, on top of the speaker close to the little triangle window. I kept the video cable so that in future I can wire it to the front double din stereo/display. Wiring up the camera and display are pretty straightforward, took me about 2 hours (taking my time ensuring everything is being done properly). Only downside it the display is a mirror image hence left is right, right is left as the screen is meant to be placed facing the rear of my zed rather than front in my case. But my aim is to aid me when I reverse my zed, ensuring I don't hit anything.
Sorry I don't have the spec you needed. I'm sure someone here has a zed with OEM reverse sensor. However, if you struggle, my colleague who has a zed has OEM reverse sensor (4 sensors I think) I can go take some measurements for you and some pics.