my only other issue will be finding a way to route the coax from that location to the radio. not sure if I want to drill a hole in the rear of my tub or just run it under the tub towards the front and bring it up through a pre existing hole and into the cab. drilling a hole means drilling a BIG hole to get the coax screw on end through and i'm not too keen on that.
1) there are coax connectors available which have a smaller core that threads into the larger PL259 style connector. This makes it easier to feed through smaller holes. Check with FireStik and Ham Radio Outlet (HamRadio.com) for those.
2) Soldering your own connectors on eliminates the issue of getting a connector through a hole. If the coax fits through, you're golden.
3) you don't need to drill any holes to wire an antenna on the tailgate (or above the right tail light, for that matter). If you use the typical small dia. CB coax, you can feed it right through the same grommet where the wires for the CHMSL exit the tailgate. Route your coax through the tailgate, exiting inside that ~3" wide horizontal plastic cover. Run it along the inside of that cover and into the right-hand side of the tub, right along with the factory harness. You can then run it under the carpet and to wherever you decide you want to mount the radio. Just be sure you don't coil any excess coax. Let it lay as straight as possible. Coils create an electrical impedance and can affect your power out (and thus your SWR).
@OP, my CB (at the moment) is a Midland 75-822 on a 4' FireStik. I have not had the power output issues that White13JKUR mentioned, but I will agree with his assessment on the controls. It is not "mounted" because I do not use it that often. I just pull it out of the console for a trail ride and put it away when I'm done.
If/when I upgrade, unless something I like better becomes available, I'll likely go to the Uniden Bearcat 980SSB that CamoCop is using. Mounting is up in the air at this point, but with the Poison Spyder roll cage, there are lots of options.
I won't be mounting it over the mirror (although I think that's a good choice) because, 1) at the moment my Yaesu FT857D control head is mounted there, 2) at some point I'll be adding an sPod, so the switches will have to go there. At that point the Yaesu head will come down to the dash bar for the roll cage.