Advice Needed - Exhaust Manifold Leak

Syleng1 said
The other option is an uneven stud. So the side that screws into the head is one size larger. 3/8” and it is about 3/4” long then drops down to 5/16” with a 2” length. With the un threaded part it’s like 3” long. You can drill out the hole to retap a 3/8” stud. Places like Mc Masters or Granger have them.
Just another option from helicoil. If you don’t like helicoils. I mean what’s not to like- they saved my butt a few times. Just make sure you get the length correct or you bottom out before the stud is all the way in.

I think this is the option I would choose. The reason is because a helicoil there is tricky. Since it goes into water, you need sealant on both sides of the helicoil. You cannot do that on the outside of the helicoil. It needs thread locker to keep the helicoil in place. Thread locker is not a sealer and it might leak around the helicoil. If you tap it up to 3/8 and us a reduced stud as Syleng suggested, you won't have that worry.