Alright, the Sakura FF geardiff fits M05/M06.

Just put mine together, and with some modifications it fits right in, at the end cover i took off the lip and filled it with #5000 Green Tamiya diff oil.

I decided to mount it into my M05, after a full nights racing not a drop has leaked and very happy with the smooth diff action it has. Same tension in diff for entire evening of racing.

Now the wait is for one more to add to my M06...