There are not many places to mount things on or under the Dash of an Alpine.
I mounted a VMS 200 under the Dash and it is bigger than the CB Radio. You can also explore the idea of placing it on the cover over the steering column, or on the wall of the Coach, or even on the bottom of the overhead cabinets.
I found the wiring and Coax cable under the dash which made it easy to install. I hope this helps with some ideas. I purchased a 75WX Cobra CB Radio and since the controls are in the Mike it was easy to hide the rest behind the dash.
Have a Happy New Year