I chipped away the undercoating only to find three rusty studs with essentially no threads. The studs look welded through the footwell perhaps? I tried hammering gently from the bottom and they aren’t budging. Is all hope gone?

 

Just use some self tapping screws

 

Or chase the threads on those studs with a die.

 

Was thinking the same

 

That’s how mine looked when I installed my junk yard flaps. They heal on for 5 yrs. They gone now though after my slider install. You want them?

 

The studs looked like those? How'd you salvage the threads?