Depends on whether or not it's poly or metal. On a doorslammer with a metal tank, all you need is a locking cap (NON-VENTED), a vent line to outside the car and make sure the tank is grounded to the frame with your mounting bolts. The trunk will need to be sealed off from the driver's compartment with sheet metal, either 0.024" steel or 0.032" aluminum, including the shelf panel. The metal tank can be altogether in the trunk or part of it can be outside the trunk sheet metal with no further protection.

A poly tank is a different animal. If it is mounted totally in the trunk, then a locking cap (NON-VENTED) and ground wire from the metal ring which surrounds the fill to a frame member will work. Again, the driver's compartment must be sealed from the trunk with sheet metal, including the shelf panel. If part of the poly tank sticks through the trunk floor, it must be covered with 0.024" steel or 0.032" aluminum on the front, sides and bottom with the exception of the area where the sump is and the supply and return lines hook up. The idea here is that while the metal tank can take a hit from rocks or other debris thrown up by the tires, the poly tank may not be able to take the same hit without rupturing.

You will not have to worry about isolating the tank from the driver's compartment because there is no way to do it. Just vent the tank to the bottom of the car, run your ground wire if it's poly, use a locking (NON-VENTED) cap and build the metal box around it if it's poly and sticks through to where it could be damaged by rocks or debris. You may want to investigate the use of an automatic shutoff valve on the vent line in the event you get upside down. I can only imagine what it would be like to be upside down with my bell rung and start smelling fuel.