ditto what the others said.
you can torch or drill the ring gear then split with a cold chissle. die grinder can do it too.. just stay outta the flywheel.
freeze the fw and heat the ring gear and drop on and tap into place. .. that usually works if you are lucky. might take you a few tries if you aren't lucky.. like me.. :)
a weed burner on a hot dog tank can help a bit. so can a thick pair of welding gloves and welding or blacksmithing tongs.. i usually keep a soft maul like brass or copper for pounding things on i don't want to really deform if things go sideways.
last thing I had to heat and install was a crank pulley for my farmall C... it fought me off ( had to split the hub after braking the pulley flange and then the new one fought me on...