even in 100+ degree heat, 90 weight oil will NOT dry up. it looks like it was ran dry due to some sort of leak. It appears that a spring clip or something failed and allowing the front drive gear to slip into contact with the main running gear at speed, either way some how it got shifted into 4 wheel hi (or low) because of the main damage is to the front and lower parts of the T-case, that was sheared downward by the front drive line. The rear drive line still appears to be attached to to the main shaft and that portion of the case is still attached to the transmission.
In either case a junk yard replacement is a good choice, I would still pull both diff covers and check the ring and pinion for any damage as checking all the u-joints and yokes for some sort of stress cracks. It would be also advisable that you drop the transmission and do a magna-flux inspection of the transmission housing or a red dye penetrate inspection. In that kind of breakage the forces are tremendous and cask iron and cast aluminum isn't that well known to like side shear forces.
Either way keep us informed