If using all-thread, remember that hardware and auto parts store all-thread is typically Grade 2. You need to go to somewhere like Grainger or a specialty supplier to get a heavier grade.
Re: The cylinder head replacement story begins…
I would look at putting thread inserts in those oversized holes. Heli-Coil type inserts may work but there are ones called Timecert that is slightly bigger diameter than the others.
These are a bit rough but free to anyone who picks them up. Also have a deck lid and a front bumper. I’m cleaning out a storage building and not hauling these to New Mexico. 505-506-5783