Yes I am thinking this tractor will be a "good one" one day, expect to have it running this year and out in the field to work, the tinwork is all bashed very badly, so new fenders hood and tanks are waiting, fan shroud is in A*****er from Ervin right now, so I think long term this tractor is going to get painted. The radiator is having a new core right now and the top tank was packed full of mice nesting material, the cap had been left off and they have been busy in there, you must have some broody mice in MN!!!!
With regard to getting the engine out without the gearbox I do not beleive this is possible, as the baffle plate in front of the flywheel will not allow the flywheel to come forward enough to release the input shaft from the pilot bearing when the front of the engine is lifted up, there are not many more bolts to take out and it seems as easy to me to lift both engine and gearbox out together and then split them., this one was seized in the pilot bearing and shaft and took a lot of prying apart.
I have seen some u frames where that centre baffle has had the gas torch treatment and cut to the diameter of the flywheel to let it come through.
I think your gearbox oil thrower gear has been damaged whilst out of the tractor, no force on that when it is turning in the box and the bottom tooth very vulnerable when sitting on the ground or bench out of the frame.