How is the nut held in place for the bolt that holds the fog light bracket to the body?
I think someone has changed mine in the past as one uses a bolt and the other side a allen screw. Problem is if they get loose the nut in the back is not secured or tack welded in place.
Can a person take out the pop up headlights to get acces to the nut in the back to spot weld them in place?

They should have the threaded nut tack welded to the backside of the body panel, but if the PO removed them, then you'll have to reach up behind the bumper & inboard of where the 2 bumper mounting bolts are located. You could re-weld the proper size up in there to make it easier in the future (they used the typical square bolt of approp. thread/diameter).

The red arrow in the pic below shows where it is on my 73 (same 70-74 & 75-76 are different).

The headlights have a welded in drain pan under them, so removing the headlights doesn't help for access to much of anything.

Click to view attachment

I don't believe it's tack welded. If I recall it's a square nut sandwiched between body panels for a "float" for adjustment purposes.

Could be wrong.

If its bolted on and works OK, I'd just go back to it... then again, if there's significant rust, you may want to get in there anyway....