[dsraven]

you can use relays to power the fuse box. the relays get energized by the ign switch when the switch gets turned to the on position. this in turn powers on the fuse box through the relay(s). same for the headlights. use a relay that gets energized to turn on when you turn the lights on. the headlight switch only passes a minimal amount of power that way so it will last way longer. same for the ign switch. the fuse box has it's own power supply(s) with heavy duty fuses or fusible links next to the battery. you can do the same for the heater motor as they also have quite a draw.