Frame nut for bumper bracket missing

[rftroy]

I have a nut missing where the bumper bracket bolts on to the frame of my 70 Challenger.
Frame rail is solid.  Looks like someone didn't think they needed penetrating oil and tried to muscle off a rusted bolt, breaking the nut away.

The missing nut is from the lower right hole.

Anyone done this repair before?  Is the correct nut made?
The frame rail is closed, so there doesn't appear to be a path to getting a new nut inside.  Plus, it would be hard to get the inside of the rail clean enough for welding.

Cut a section out, weld on a nut, and weld the section back on?

Anyone have  a better way to fix it?

Thanks,
Robert

[anlauto]

Hog the hole out enough so you can fit a regular nut inside it. Position it flush with the frame rail, then weld it in solid. Grind the outside flush, clean it up with a tap and you're good to go !

[larry4406]

Yep - what Alan said