Kohler command 12.5

Working on a miller welder/generator with a Kohler. Found several issues but the one I’m looking to address currently is on the cylinder head. Where the muffler attaches to the head around the carb side bolt threads it’s all “washed out” by exhaust gases I’m guessing.
Could I repair this with some steel putty?
Is this a sign of a blown head gasket?
Is this a sign of issues with the exhaust valve?
The muffler mounting bolts were really loose

Having issues posting pictures but the issue is not with the muffler, it’s with the cylinder head where the muffler mounts to the head. It’s missing metal around one of the bolt holes. Kohler Ch12.5S I believe is the model number. And no studs, bolts go through muffler and into the head

Yea I’m not to sure bout the JB weld idea either but I did buy something they make called extreme heat. It’s like a hardening epoxy paste product that is supposed to be good for 1000 degrees and lists exhaust’s as something it’s used for. May try it for chits and giggles. I can’t weld aluminum and would have to take it to someone for that repair. Mainly trying to get this thing running to verify power output from weld leads and the 110 receptacles before diving any deeper or sinking much money into it. It’s 1995 Miller Bluestar 180k with about 700 hours on the clock