If I had to do this on my own truck, here is what I would do. Drop the tank, find a good place to drill a hole in it, put a nipple in the hole, attach a piece of rubber hose to the nipple and run it up to the same height as the filler neck, up under the body. Then put a goose neck in the hose with a fine mesh screen over the end with a pipe clamp, and bango, you got your self one vented gas tank that looks just fine, and no one will ever see the vent. Just what I would do, you may not like to do it that way, as you said you are not keen in just drilling a hole in it, but....this is more than JUST drilling a hole, it is making it more functional. Ain't that what we are all about? Making our rides a little more what we need and want?

Just my opinion.