That's what I did, I was having a small vent issue when I switched to EFI. I drilled a hole through the inner piece and all my issues went away. Probably not the best solution, but it worked and cost nothing.
Running a vented (drilled) cap on a Mopar with a fender filler like these all use is an invitation for gas down the side of your paint job. If you are not using the canister, and the rest of the system is intact, all you really need do is to run the front tube "up high" and either end it "overboard" or plumb it into the air filter bonnet. An alternative is to "build" a likeness of the 69/ earlier vent tube in the filler neck.
All that needs happen for fuel all over the side is a full tank, a hot day, and parking someplace like on a one way street with the filler side of the car tilted low.
