http://www.oople.com/rc/manuals/zx5/...s/zx50007.html
Oneway diff has 2 oneway bearings with the outdrives (part 89) sitting in the bearing, we used this once (on original kit car), broke a front wishbone and lost the outdrive forcing a return to a standard diff. We always had a oneway on the shaft.
(I think some of the parts came in the original kit, only needing to add extra bearings & outdrives, one of the attractions of the original kit, came with the diff & oneway options - in the box)