I need a way to sleep in an enclosed space with a can of gasoline...?

You need fresh air and ventilation...even if you take the gasoline out of the equation. Not quite sure why you would want to sleep in a trunk instead of a seat... I assume you have a two seater with an enormous trunk. Maybe you should consider buying a delivery van or better still a small camper-van or day van. If you get something in good condition you won't loose a lot on resale when you have finished with it. Sleeping on a proper mattress makes such a difference...and you will need a good nights sleep.