I upgraded my Allegro Bus to the Sony setup. It originally came with an ADTH brand monitor/camera. It had a nice wide field of vision but not much resolution and specular highlights off the toad's hood caused excessive vertical streaking so I dumped it. I picked up a Sony color LCD monitor ands camera from
Riverpark, which is where lots of RV manufacturers get them from.
The Sony monitor was a direct replacement for the ADTH as far as dash knock-out size goes. If your previous monitor is smaller, it shouldn't be a big deal to upsize the hole to fit. The LCS monitor is a little over 1" thick, so the mounting bracket wound up pretty close to the dash compared to the old deeper ADTH monitor. That meant I had to make a place to set the new mounting bracket on. Not a big deal, really.
The Sony monitor is capable of accepting 3 different camera inputs and is typically used with the side mounted bullet cams that connect to the turn signals. I didn't go that way because I really didn't want to lose my rear view monitor right when I'm ready to make a lane change back into my lane after a passing maneuver.
I can't believe that the Sony cameras aren't made any more. I'd check with Riverpark on that one to confirm price and availability.
The Sony camera/monitor is an awesome setup. It has great resolution, wide field of vision, and good low light capabilities. I didn't think that the color versus B/W issue was that big of a deal though at first. But, now that I have it, I like it. The human eye is used to seeing things in color. I can take a quick glance at the monitor and my brain instantly recognizes what it just saw. With the black and white system it does take an extra second or so for the brain to "decode" what it just saw. That extra second staring at the screen takes away from looking where you are going and my RV will cover lots of ground in one second at 70 MPH. Plus, it's kind of cool to look back there and actually see yellow traffic lines, green grass, etc as you drive.
By the way, the color Sony setup comes with a 65' cable. You'll need it because it's a 6 wire cable, versus the 4 wire that is typically used so you cannot reuse the old cable.