Could you get Mike to make you a dogbone and cup for the rear end? Get flat spots put on the cup, so the brake pads can be put on it like usual and put the cup on the rear diff pinion . Then take your plastic rear center diff mount that got replaced by the rcm motor mount and bolt that in front of the rear diff to hold the brake cam and linkages. Basically shift the rear brakes to the rear diff. Don't know hard it will be to do, I guess it will depend on your layout, but it could be worth looking at if the spacer thing doesn't end up how you'd like.
You could probably keep your rear cvd, but just flip it around and use one of Mike's
1/8th diff output shafts on the center diff.