I'm guessing your existing setup has the 21 spline gear case?
If you want two cases with stock gear ratios, buy the 23 spline r10 adapter and a 23 spline input gear for the rear case. $660 plus shipping. If your going that far, I'd recommend 4.7 gears in the back case(which are on sale now). $900 for gears and adapter. I'd save and do it all at once. I have a mc08 r10 adapter and love it. I'm sold on the rotated adapters.
