I pulled the bed cover off and exposed the floor pan behind the back glass. I need to replace some of the sheet metal because its rusted out. The panels don't seem to match up with anything in the OPG, Danchuk, Ausleys or Year One catalogs. I thought the floor pans are identical to Chevelles, but obviously I'm wrong!

I don't think they are available at any of the parts suppliers. :-( You need to find another elky, station wagon donor car, (back seat pans), or fabricate your own.
Good luck!

I'm doing it surically by removing the worst rust. Then taking a panel beater (plastic mallet) and lead shot filled leather bag to try and get sheet metal into the same shape as the piece I cut out. Mig welding in the patches and lots of grinding. While I doubt this car will ever be show worthy, I want to do the best that I can for her.