useable diff or not?

[Big Vern]

The pictures you supplied in your original post show a normal open diff! At a pinch it could be a viscous coupled diff as was used in the Sierra 4x4 I had many years ago. (though I don't see the Viscous part only the planet gears and sun wheels) The viscous coupled diff is NOT an LSD and doesn't work in the same way as an LSD!
The 4x4 I had many years ago also had a Turbo nailed to it so it went like stink BUT all of the viscous drives in the system could be made to slip during a hard launch causing embarrassment and not a lot of go....
The rear wheels could be made to turn in opposite directions though with more resistance than a fully open diff. A true LSD this would be almost impossible!
The viscous diff will probably ok for what you need but repeated overheating will kill it and I once had quite a graveyard of dead viscous diffs!!!