Mounting CB (or other) antennas to a drop-in tool box is an acceptable option so long as the installer follows a couple of simple rules.
First of all, if the antenna being used is a standard ground-plane dependent antenna, the toolbox MUST be grounded to the vehicle. In most cases a short wire (at least 12 gauge) or grounding braid may be attached to the front side corner of the toolbox and to the underside of the left or right side bed rail. On that note, do not make the wire any longer than necessary as wires that are too long can become an active element in the antenna system. The other issue to take note of is that some beds on some pick-ups are not grounded to the chassis. We have never seen this on American-made trucks but have, on several occasions, seen it on non-American-made vehicles. If there is no ground between the bed and the chassis you will need to run a grounding wire or braid from the bed to the frame of the vehicle.
No-ground-plane antennas do not require the toolbox to be grounded but the location of the antenna is every bit as critical to performance as is the antenna used on a ground plane dependent system. Unobstructed air space around the vertical antenna mast is the best scenario for transmitting antennas.
The two most popular mounting configurations would be the standard side mounted "L" bracket or the top-mounted dome or roof mount. In any case, for best performance we recommend that you place the mount as far away from the vehicle cab as possible. Mounting transmit antennas too close to other vertical surfaces restricts the antennas ability to radiate its energy and can cause unacceptable SWR problems. For optimum performance, use antennas that are at least 4ft (1.2m) in length.