its not a case of how much bhp an mt75 can handle,its the torque which is the important factor.anything over 350 ftlbs of torque is pushing the mt75.I have sheared of 3rd gear teeth with well over 400ftlbs of torque but my car has only 300 bhp.
personally i dont think its the front diff case that is a problem,it's the strength of crown and pinion teeth.how can fitting plate make the gears stronger!! the gears break off then wedge themselves between the crown and pinion, then it breaks the diffcase.