For the Sals you can add the TJM Pro-Locker, or at least they list it as available now.
Also the Kaiser locker from Brazil is an auto locker that is made to fit the Sals, but you'd have to privately import one.
How It Works - KAISER - Differential Locker
It should be much, much smoother than a NoSpin/Detroit, it looks very similar to the Weissmann locker that was the darling of the Indycar/F1/Prototype Sports Car scene through the seventies and eighties until active hydraulic diffs became available.

