Why get rid of the exhaust? The factory AE112 exhaust is way better than the AE102 (extractors straight from factory rather than a cast-iron manifold for one). Don't quote me on this, but the computers _should_ be swappable, the later engine doesn't have any extra sensors or the like (plugs may be slightly different), but the tune may be different (there are slightly different power/torque figures for the AE112 compared to the AE102, some of that will be down to the exhaust but some would be in the ECU). If you just swap in the long motor and re-use all the AE102 sensors and wiring then I can't see it being too much of a drama.