I heard about these from gene hickerson he is a Factory cen driver. He helped design there car & truggy. Here is a pic clik on the link & stoll 2/3 of the way down on the left.
I dont think a fully locked center would be the ticket, hard on parts....you need a good slipper for that. With the center diff you can get away without a slipper pretty easily, since you just need to power the single easiest wheel to spin.