Holy crap!:o
Don;t do D !
I think C would be the best, although it's the most work.
They should construct spark plug threads to be softer the alluminum heads!

I am not ASE cert. or anything, but I would imagine the distance of the spark plug electrode is rather important for proper A/F burnage" or whatever you call it. It also should be threaded down there pretty good to hold up the the compression.
Goodluck