49 geezer
I think all the Offy 2x1, 3x1 intakes that came/come, from Tom Langdon's Stovebolt Co. already has the plugs welded in them. He is the only supplier that does this. He really should state that in his advertiseing. It may help others to buy from him. ???
Anyway it sounds like you will have a non-leaker when you get finished with your project.
I just wanted to give you a heads-up on what could happen. Better before than after.
Good Luck !
Ed