Question About Seat Prices and Compatability

Hi guys I am looking for a rear seat for my 66 Valiant 2 door. I am curious what other models will fit like a Dart or Cuda of the same year or do I have to stick with Valiant seats?

I also have a set of seats for a 66 valiant convertable front split bench and matching rear in very good condition, mint color with dark green inserts. The rear doesnt fit my car as it is to narrow and I have buckets in the front so no need for the split bench. So my question is what are a set of matching seats worth for a convertable in very good condition. I would think that rag top seats would be harder to find, but just not sure what to ask for them.
Thanks in advance,
Paul