Not too sure from the pics but it looks like the fill plug is very close to the shift rails. If it is its a dana 300, if the fill plug is lower to the right of the shift rail its a dana 20 but it looks to be a 300 so your a lucky SOB. 
2.46 lowrange stock but you can grab pretty much any upgrades you want, 32 spline outputs 3.57 and 4:1 lowrange gears etc etc.
The casting on the Tcase says c300 if that means anything and the trans says t19-148.
