I'd be a bit leery about that differential housing if the whole spider gear fell out. That means the spider shaft must have broken or something else gave out for it to fall out.
It might be easier to look for a complete pumpkin.torque tube assembly. At a minimum, I would replace all the bearings and the ring & pinion as well as the spider and side gears. It would be easier in the long run to change out the R&P with a taller gear set without having gather up replacements for the parts that are suspect.
