Easiest replacement is factory 250/300 rearsets. Direct bolt-in.
There's two springs to deal with. One is pedal return-spring and other is brake-light switch spring. Typically with aftermarket rear-sets, you also have to flip master-cylinder backwards as well. Post photo of how you have things installed and what's left over.
See step-by-step guide here:
https://www.ninjette.org/forums/showthread.php?t=14945
Also this video
Link to original page on YouTube.