Spare Tire Bolt Removal

[Atlantic28]

Got a side-mount spare on my 29 CCPU. One of the bolts that holds the spare has threads that are worn to the point that a lug nut will not hold securely.

The bolt has a square section where it passes through the plate. Can't tell if it is swedged or not, but tapping on it did not seem to move it. Should I smack it with a 3 lb hammer, use heat, or ??? How do these bolts get held in place?
Doug