A U-shaped tube teed into the filler neck that rises above the level of the fill cap and then finds its way to the outside of the vehicle would be the simplest way to achieve a good vent. The charcoal canister and purge system is just lipstick on a pig- - - -something the tree huggers insisted on in the 1970's that had no real purpose other than self righteous virtue signaling.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!