I have one mounted just above the dash so the view clears the wipers. I have another one that I am going to install in the rear window. It will require installing a 12v outlet near one of the overhead lights to supply the 12v.
If you get a dash cam with a battery, you may want to consider making a sun shade for it as I have read the battery is the first item to fail from heat. Or you can get a cam that has capacitor only which is not so prone to failure from the heat.
The brand I have is VIOFO A119 with capacitor, which is available with or without GPS. I bought an extra GPS, the part that mounts to the windshield, so I could use the cam in my car and the Vegas. I think I paid ~$70 with GPS for the cam and ~$14 for an extra GPS on ebay.
2015 Thor Vegas 24.1 in Ocala