rcborst,
1). Inverters work ok as long as you stay under their rated amps. Not really needed for tailights. Change out the insided holder and go to a larger bulb. sorry forgot the size bulb but it is still 6 volts.
2). I would only use an inverter if trying to go to 12 volt tailights.
3). YES - This is the major item to do if staying with 6 volts. It will accomplish two things, make the headlights brighter and save the headlight switch under the dash. This is caused by the switch only drawing the current required to pull in the relay (low current thru switch).
4). With 6 volt system one of the main items to stay on top of is keeping the grounds clean on both the battery and the frame of the truck.
