Do you still use the fiberglass top?
e.g. there is a problem here, in that the gas tank will now be "inside" the same space (air) that you occupy. not terribly safe, aside from fires, any type leak will have bad fume problems for you. Remember, that thing has to be vented.
Now if you have permanently ditched the top so everything is open all teh time, probably less worry.
Unfortunately in a 4Runner there aren't many places for it to go.