What kind of dvr dash cam system are you running?
It's a K1S (
Amazon link). It's a 2 camera system that records to an SD card stuck up the arse of the above pictured remote mount DVR unit. Records @ 30fps in Glorious 1080p.
I quite like it. It's set up to automatically start recording when you start the truck, and automatically stop when you turn the engine off. When it starts up, the display turns on for 1 minute, just so you know it's recording, then turns off (you can adjust the time-out).
My front-facing camera is behind the center mirror:
The rear camera is on the rear hatch, just inside the rear window:
The wires for both cameras run from the center console, behind the dash, and up the A-pillar. The front camera wire runs inside the roof structure that runs along the top of the windshield. The rear cam wire (which is Quite Long) runs to the rear within the roof structure along the drivers side, then goes through the rubber snorkus that contains the factory harness for the central locking & rear wiper. I notched the plastic trim above the rear glass to allow the wire to exit.
The unit's power wire is spliced into the ignition-switched lead for the stereo. This is how the unit knows when to start & stop recording. It's got an internal battery so it can gracefully stop recording and close out the video files when it looses power.
Do let me know if you've got any other questions.