There's actually a lot of room behind the instrument panel of a '65-'66 Mustang, but finding a place to locate the RediRad can be tough. Distance from the radio is limited by the short antenna cable leads. We chose to mount our RediRad to the side of the glovebox with industrial strength Velcro. Double-sticky tape, or even small screws with nuts, can also be used. On convertibles, you can mount to the underdash brace with the supplied wire-ties.