I don't have a disconnect switch, but that is not a bad idea.
On large equipment, and this should pertain to trucks, too, the switch is located in the hot lead, not the ground, between the battery and the first place the hot battery cable is connected.
Negative ground systems have the switch on the positive cable. Locate the switch where it is convenient, but away from anywhere you could accidentally ground the hot connection on the switch.
Even if you have a disconnect switch in the line, it is still a better idea to remove the positive (hot) cable connection at the battery to work on the electrical system.
The biggest drawback to "disconnect" or "kill switches" is that they introduce a very small resistance and voltage drop in the circuit.
Not usually a problem, but once, we were trying to start a BIG piece of equipment that didn't want to start, and things started getting warm. The disconnect switch was a lot hotter than the cables, and I could feel the heat int he cable through a pair of leather work gloves.
