so you've unbolted it from the diff,and the rear section isn't touching the diff anymore its facing the floor the mount is removed and the input shaft is ceased to the gear box ?
so its rusted on or the splines are crunched on the input shaft, last resort if your sure only the input shaft is held in by the gearbox then put a tow rope on the tail shaft and on a car pull it out, slowly, TAKE CAR OFF THE STANDS, JACK SO ITS BACK ON ITS WHEELS if you attempt to do this
other then that tow truck and to the mechanic