With a truck you do have some issues, though thats almost true with any dashcam and any vehicle.
With the cabin mounted camera the bed of the truck will block a bit of the view out back, and if cars where you are have front plates, they will be too far off to read when you can see it on the camera.'
you are often forced to mount off the headliner as a truck might have a sliding party of the back window or in this case what appear to be the whole window being electric, so you cant really mount off the glass in a traditional way.
On the + side if you have parking guard, the camera will cover everything lying in the bed of your truck.
Alternative some brands provide a waterproof camera unit you can put all the way out back, but then it is exposed to the elements, and at least the truck i drove around the turn of the century accumulated a lot of dirt back there, though mine also had a hard top over the bed.
So you probably need to clean that camera often to have any chance of getting detail
Today i saw a guy that had stopped to help a elderly couple with a flat tire, so i in turn had to pull over too and check up on some things, and turn out he was not related to the couple just a helpful guy, so for his efford he got a thumbs up from me before i left.