I did the swap on my '01 520 MXC to a SX tank, shrouds and seat. You need to choose EXC or SX. The SX seat is different and must be used with the SX tank. If you go EXC you can use the same seat you have, you'll just need the shrouds and tank. I don't recall the exact prices but I know the shrouds were around $30/each. Either way don't forget to order or buy screws for the shrouds since you don't have any on a MXC. Good luck.