'68 Coronet R/T wrote:A lot of good information there.
Bottom line for your particular situation is to cut that portion of metal out and make a patch to weld in.
Think about your patch and the placement of your seams. Try to get the seams located where you have good access and sufficient metal for welding. Make your patches to fit nice and snug into the openings as well.
I found it much easier to learn proper welder setting by practicing on odd pieces of metal.
Start with the recommended settings for your welder on that thickness of metal and see what you get. A porous mound of metal may require more heat or less wire feed.
There are videos out there that go into detail on setting up a MIG.
I've already have my donor patch. Just need the time to install it.