Hi Brian,
If your 75 had a bench seat from the factory, there aren't any bucket seats (not even original Nova buckets) that will be a direct bolt-in swap. That's because the factory bucket seat Novas had some special mounting adpaters welded to the floor pan.
Since you'll have to make some mounting adapters anyway, you can use bucket seats from most any car. If you want something relatively factory looking, I believe 2nd gen Camaro/Firebird seats are pretty similar in style to the original Nova buckets.