Heat loosens rust no matter how you apply it-
as long as things shrink and expand, the interface
between them moves, and breaks up the rust.
Took me a while to figure that- if you heat the b'jeezuz
out of the bolt, it'll expand in the hole, then shrink as it cools.
If you hope to remove the bolt, you then quench it to harden and
shock it. If you hope to drill, let it cool slowly so it stays soft.
However, heating here might be a recipe for setting the car on fire,
as it's coated in undercoating, and that stuff burns.
I have used an air body saw in a similar predicament- even if
you cut into the threads in the car, it'll only make a narrow groove,
so they aren't structurally compromised.
The body saw blades break easily, but they're tiny, so they can
get into places like this.
Also a round file, but that will take... hours. Even with
a power filer.
Or another TINY hole in the thick side.
And hitting it. A lot. Because like heat, shock breaks things loose.
Like my sanity.
t
cracked