Exhaust studs just spin

[Shadowfire]

The correct fix for the stripped out head, is to install appropriate Heli-Coils into the head (something along the lines of https://www.amazon.com/Helicoil-5546.../dp/B0002SREP4).

This means taking the head off, since you have to drill out and tap the old holes.

Also, JB weld on an engine head (especially around the exhaust port) will be subject to temperatures that will destroy it. At this point, running a tap through the holes is not going to renew them; there is obviously missing metal, which the tap won't fix.