Plumbing a '69 style filler neck vent

I'm replacing the fuel lines on my 73 dart - but the vent line that used to run to the charcoal canister is now going to be a vapor return line - so I'll need a different vent. I've seen suggested here many times that users could add a '69 style vent to the filler tube, plumb a loop up high from there, and back down through to the exterior. I'll be pulling the neck to do this but I have the following questions: Is it necessary to have someone weld a fitting to the neck or can I simply drill a hole and add a fitting thats threaded on the inside and secured w/ a nut? If I go that route I'm guessing just a thicker rubber washer/gasket will provide a good enough seal even with the fitting being added to a round pipe? And lastly - would there be any benefit to adding a charcoal canister in the truck to plumb the vent through prior to routing it to the exterior? I'm thinking it would help w/ fumes in the garage, which haven't been an issue - but not sure if this new system would cause more fumes. I also am trying to keep the engine bay as clean as possible and would not like to add one there. From what I read it seems like the canisters needed a vacuum to release vapors back to the tank as originally designed but maybe I'm reading that wrong. Any help would be appreciated.