I have pulled all the parts from my mx3.
Some fat guy sat in the right seat and the belt never made it over him.
Since then the seat belt never retracted properly.
I have a new rail for the right side but I am not sure whether its the track or cablin that needs to be replaced.
You can have it all for 150 plus shipping. That includes all trim pieces, belts, tracks and one new replacement track, the unit under the seat, the center console and lap belts and their mount.
You will need to trim your headliner smaller for this to fit as well.
Shipping will be expensive depending on where you are located.