Here is a prototype of the Revo hybrid diff cases. The final details are being worked out, but the plan is to allow use of the stock driveshafts(or aftermarket cvds that fit the stock diffs). Enjoy. :)
I would guess around $100 per diff setup. The diffs already cost $65ish, not counting the custom modded pinion shaft and output drive shafts(to accept stock diffs). We are still working out some details on the procedure.