I put a 4L80 behind my big block in a B body. I had to do minimal trimming. I fabbed a new rear crossmember. Had to cut and move the right collector on my underchassis TTI headers. I have a wilcap and a TCI adapter. Chrysler mini starter in stock location. Turbo 400 is a little smaller than the 4L-80. All in all a pretty easy conversion. Galen