"Replacing a ring gear involves destroying the old gear" - Not true.
The ring gear can easily be removed without damage to the parts. You must
use a large brass drift (1.5 to 2" in diameter) and substantial hammer
against the ring gear. Using a brass drift prevents any damage to the ring
gear. Set the flywheel on a platform so that the flywheel is supported but
not the ring gear.
To reinstall the ring gear, heat it with a plumber's torch. The ring gear
does not have to be red but it should start to discolor as it expands. It is
not necessary to cool the flywheel. Carefully align the ring gear and slip
it in place. Do not drop it, as you do not want it to bounce. If it does
not fully seat, you can use the brass drift to tap the ring gear home.
I have replaced many, many ring gears using these methods.