Help! Mugen Mbx6t with Slipperential

Hi,
I am trying to mount a 50T slipperential into Mbx6t.
However, I have two situations. First, the 50T spur is so large that the gear makes contact with the chassis. I believe the solution is to use a 46T spur but all I've got is 50T spurs.
Second, the thrust bearing also makes slight contact with the chassis . I think this comes form the motor mount that pushes Slipperiental a little bit forward and force the thrust bearing to touch the front edge of the chassis hole.
Do you have these problems? How do you solve them?
Thanks!