Matt,
I own both a C14 and a ZX14. The seats "DO" interchange. Here is the catch, you have to order the metal alignment bracket as well as the latch bracket from the oposite bike. They just unbolt and rebolt on. I tried it today. Putting the ZX14 seat on a C14 looks like it would really help riders that are vertically challenged more easily touch the ground. The underside of both seats (hard plastic part) are identical.
Hope that helps.
Thanks,
Chris