As part of the new fuel system design, we previously planned to repurpose the driver side rear fuel cap as a hidden (and locked) battery cutoff switch. The fuel cap housing was machined to fit the cutoff switch and glued in place.
The switch itself is located where the left side fuel tanks used to be.
Two pigtails are required to engage the switch. One enters the trunk side wall from the battery’s negative terminal and the other returns to another point on the side wall grounded to the chassis (the battery is located in the trunk).
A bulkhead pass-through insures that the incoming cable from the battery’s negative terminal is not grounded to the chassis until after it passes through the switch.
Because the battery has been relocated to the trunk, the distance to the starter is now about 10 feet, and this requires a 1/0 AWG cable to insure sufficient current capacity. It’s good practice to balance the cable sizes from the negative and positive terminals, so 1/0 AWG cable is also used for the negative terminal cabling even though the distance to the chassis ground point is rather short.