A518 in a 68 Dart?

How about this, how would the new Hemi electronic trans fit? I have seen some A-bodies with a new Hemi, anybody know which trans they are using. I am asking because if I swap in a new hemi like I want to, it will come with the trans. I have seen pictures of it and it looks slightly smaller than the 500/518. I am desperate to get an overdrive auti in my car, but I dont want to cut the floorboards.