They make wireless versions, btw
Can you get to that area from the inside? Thats how we did ours on our MCVI7. heck above the bed and see if you have access, then run the wires down the top inside to the front.
https://typesauto.com/collections/backup-cameras
Wireless setups don't like to transmit thru steel and aluminum. I ran my cables on the floor and above in the bays all the way to the engine compartment. lvmci...
These seem to list a distance of 30 feet. Do you have any experience with one working 35+ feet from camera to monitor on a bus? I looked at lots of cameras designed for cars but at the time couldn't find one that would covert the distance without the transmitter mounted inside. Still wireless in that you don't need to run wires all the way front-to-rear, but not totally.
Don't forget to wrap the camera cables in the radiator or engine compartment in some kind of heat protection, lvmci...