Re: Arc Welding on engine muffler area?
If there is enough material left then, look up Helicoil.
You do it or a machine shop. If you do it then have the special size drill and tap for the Helicoil. Insert tool and tang breakoff tool can be improvised to save money.
Individual parts I can get a a supplier in San Jose, CA so I never spent for a whole kit setting you back a bundle.