AR-5, r-154 Anybody actually done this

I am wanting to do this on a magnum powered BMW I am building. I Know that the ma5 Colorado transmission has an input shaft about 3/8 inch longer than the ax15. Did you have any clearance issues such as the input shaft bottoming out on the pilot bearing? I have been investigating the possibility of swapping the ma5 input shaft with one from a ax15, that would make this swap easy but I cannot get a straight answer.
Personally I don't believe the claimed torque ratings on this transmission. The Supra and Lexus guys a making huge numbers with this tranny with little failures!