Air Grabber Lid

[Big John]

If it were me, I think I'd neutralize the rust and then build it back up with body lead. Eastwood sells the lead and then you'd just need a propane torch. A little bit of bondo to finish, prime and paint.

 

[Big John]

Or..... Again, neutralize the rust and use Lab Metal filler. They use that as filler for stuff that is powder coated. It is supposed to be good up to 350°F