OK, OP, I have found the simplest solution for you (I think). You will need:
- 1 four or five pin standard automotive relay
- 2 fuse holders
- 1 five amp fuse
- 1 fuse according to light power rating
- 1 three way switch (in-cab)
- 1 basic 2 way switch (tailgate override)
- 1 three way or two way waterproof switch for in-bed (depends on wiring method)
- 3 one amp diodes.
- lots of wire and connectors.
This is what I came up with. Please tell me if you notice anything wrong. Im tired and may have overlooked something. This diagram does not account for the lighting in the switch. That wiring will be determined by the switch you use. It also does not allow an override for the dome light auto activation. Only and override for tailgate. This is a ground (-) switched circuit. Here is my diagram:
There is an easier way to wire it though but I'm not sure you'll like it. Basically the diagram shown allows from the in-cab switch the lights to be off always, on always, or auto which is triggered by any door being opened, or the tailgate being dropped. The in-bed switch allows it to remain in auto (whatever the in-cab switch is set to) or off always or on always. The reason I wired it this way is so that if the lights are turned on from the interior switch and you want to temporarily turn them off from the outside, you can do so. The easier wiring I'm about to show will not allow the second in-bed switch to override the interior switch. It will only allow for you to turn the lights on anytime regardless of interior switch position. In the following diagram, changes in red indicate the new simpler wiring. The first method requires a 3 way switch in the bed and the second method requires only a basic 2 way switch for the bed. Make sure its waterproof.