It is possible to put a seat of an 1800C on to a 1300C, with some modification. The 1300 C takes a different seat then a 1300 R or S though. Many here upgrade the torture device known as the 1300C seat, I went with mustang. Others prefer Ultimate, or Saddleman, or having there stock seat modified by our artisan members such as, Robert Doer, or Mean City Cycles. There's many paths to take, Give us more information and I'm sure we will able to give you some more targeted advice.