I have the 23 spline setup, call and ask if they still sell just the 21/23 coupler
i called and they do sell it seperate, they want 150.00 plus shipping, and if i recall you wanted 200 for your adapter. thats 350, thier complete kit is 345.00, so it would be cheaper to buy a brand new set uyp with a warrenty bal bla bla