Ah now that the problem is resolved, back to the "standard/metric" blather:
Very fittingly, exactly 200 years after they declared independence, the USA went officially metric in 1976.
40 years later it seems not all got the memo.
As for pulling the engine for rethreading repair, I would just pull the cylinder.
You have the exhaust removed, 2 more nuts remove the intake, 4 head nuts - BAMMM!
Slide the head off, slide the cylinder off, WHAM! There it is in your hand, easy to work on.
Ideally you either didn't damage the gaskets, have new ones or cut some out of empty soda cans.
Slide it all back together, torque the nuts so they don't strip or loosen and SHABANG! Yer ridin'!
Steve