That’s good advice and exactly what I would go with as well - lead filling it would be a good option that is unless you have and can use a TiG welder properly. IMO you'll probably end up with quite a mess with a MiG welder, TiG is so much more controllable as you can apply heat and filler separately; it's also a finer more precision form of welding. TBH I’m not a big fan of MiG (although it certainly does have its advantages - mainly speed) but I love TiG welding.