i don't know about the tranny, but im sure people have used the s-coupe tranny with the clutch changed to 1.6 or something of that sort, but yes the beta swap on the X3 or the scoupe is really simple, i have seen 2 already at the hyundai meets in orlando, so its definately a nice swap, pretty powerful car, and if you go turbo you will be even more faster, with such a light car it makes it really fast, but its up to you and your budget and your style of how you go about things, hope that helps to inspire you a bit on the X3 beta swaps lol