Id say swap the engine, box, gear linkage,ecu and loom i would imagine, the mounts are the same, but the gear linkage is different, if you fit the MTX75 box from the RS you'll need the lift up reverse gear linkage to go with it ( only a few bolts in and out... mind the exhaust though )Ive owned several RS2000's and 2 105 bhp and 1 130bhp XR3i and stripped both (currently have the remains of a 130bhp escy in the garage ) and they are all very similar !! I work in lovely Portswood if you want to come down and look at the layout on my current RS2k