Welcome to the Photobucket "enhanced" experiance.

As long as you have a proper firewall, and the tank is vented outside the body, everything can stay in the trunk. I prefer this and haven't run anything through the floor in years. You will have to get the main line out of the trunk, under the car and up to the engine compartment. A bulkhead fitting with appropriate plumbing is best, a hole with a grommet is cheaper. Mounting depends on tank shape and size. On a real race car, I wouldn't use anything larger than 5gal. The mounting methods in the photos I see look fine. Or you may want to express your creativity.