It has a T19 trans and Tcase is a Dana 300 "I think".
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.
![Smile :)](https://board.marlincrawler.com/Smileys/marlin/smiley.gif)
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.