You are going to have to split the tractor in half just like doing a clutch job on it. If you have the overhead crane or some other way to support both halves while you roll the rear half back, then not so much of a job. Otherwise it could be a bear. You sure don't want to drop either half of it when doing the work.
Recently my brother in law was reworking an 8N Ford and worked over the starter a couple of times, bought a new one but it still would not turn the engine even though it sounded like it was engaging. Finally he noticed that the ring gear was spinning on the flywheel. Some one had attempted to weld it on to the flywheel but not succeeded. I have never seen one spin on the flywheel like that so it must have been replaced with wrong size by previous owner(s), but I fixed it by putting 4 good welds on it. Since it didn't appear to be cracked and no broken teeth, the welding fixed the issue.
That wont work for you if you have missing teeth though.
