For you guys who are more experienced with this stuff, what would be the preferred method for doing this?

I want to add a bung to an aftermarket aluminum radiator. Actually, I have 3 of them to do. I do not own a tig welder, nor do I have the skill to use one. I could buy a spool or gun setup for my mig and I also have a small tank I could use for 100% argon. But I'm considering just brazing it. I understand brazing on larger aluminum pieces can be difficult, due to heat loss. I also was thinking instead of adding a bung, i could just add material and then drill and tap to the size I want. My plan would be to clamp a small slice of 1/2" or 3/4" copper tubing to the flat area and then fill it with my brazing rod. This way, I don't have to worry about trying to get a bung sealed all the way around the joint. Maybe the aluminum rod will stick to copper though... not sure on that one.

Thoughts?