I've seen GM six bangers, including GXP, in rails, both mid and rear, but I haven't seen a SC. A bus trans probably won't hold up to the torque and I don't know how to adapt a Mendeola. The wiring would be a complete salvage. The AC compressor does not have to be removed because of the clutch. An custom IC would probably be the best bet for mid/rear engine.
If you plan on racing, the SC would put it in class 1, against 600 horse LS7's and the like.