Why the Wimberly? Does that or say a Kirk QRC-3 screw right onto the 468MG head?
The Wimberley C-12 screws right onto the 468MG, so I simply unscrewed the RC2 clamp from the 468MG head (two hex screws), and screwed on the C-12. The Kirk QRC-3 would fit on a 468MG, which has a 3/8" threaded stud, but it looks like you'd need additional parts to retrofit it onto a 468MGRC#. The Wimberley C-12 comes with the screw you need (and the allen keys in both sizes), and I like that it has three small set screws, vs. just one with the Kirk.