Yep, that's the problem with trying to get old parts here in the rust-belt. Your best bet is to try a southern dealer. There is a truck parts dealer in Geneva, Ohio called Southwestern Truck & Auto.

I've purchased aftermarket fenders there and even sold the guy some extra stuff that I had.

I doubt they have a bed for that truck, but they may be able to point you in the right direction. I can't hurt to call. I believe up to '86 will fit.

Randy