JP is right, Jim knows his stuff. For the $3000 you get both the LSD and a custom gear set of 3:91 of even a 4:1.
I spoke with Jim at length about this. I asked him what the difference between his LSD and Quaife and he gave me a bunch of info about how his equipment works and the reason it is better. Don't have my email as I am travelling or I would pass that info on, best to just email him and get a dialog going. It is best by email than phone.