That has been considered but I figured there would be reception issues with the antenna lying horizontally under the dash amongst all the wiring instead of being vertical outside the cab.

 

I doubt that would be an issue as long as there is an antenna the reception would come in pretty clear I had an old chevy truck that the radio didn't pick up any stations that's what I did to fix it, didn't have any more problems with the radio after that. by the way I hated that truck cause it really poor mpg's and I couldn't haul what I wanted