I wonder if this is something In can get an easy replacement for. I'm not really a metal fabricator, but it looks like a box with a thick piece of steel on it.
Not really a fabricator…. Not yet! Honestly you read the room correctly.
It’s a box with a reinforcement on it. That’s all it is. Break it down into smaller bites and fix it. It needs to be repaired and even if you do not fix it yourself, knowing what you need before taking it to some one who can will save you money on unnecessary additional repairs. What will happen is the part will (actually it already has) started to flex the metal a little and it will eventually break and to the point your spring is loose. It may go thru the trunk floor doing more damage or if you get hit from behind and it will not absorb the impact as well and do more damage than just the impact would had.
Do some more “search” about rust, or rot. There is a lot of info on here already. You got this!
Syleng1