The subframe for the XT/X model is very slightly wider at the front upper mounts than the S/SX as they use a different main frame. You can still fit the subframe but will have to do a bit of fettling to make it fit. You will also need the rest of the gubbins that goes with it though, such as the undertray, battery box, seat unit etc as these are not transferable between subframes.
If you can find a complete back end for sale on ebay that would be the best way to do the conversion, or even better find someone with a Ulysses that wants to convert the back end to a S/SX and do a straight swap
