Sweet ride, love the old steel steeds. You in NC?
Saddle selection is a very personal thing. What works for me may or may not work for you. It sucks but the only way to find a saddle that works for you is try different ones until one works well. The one you've got "looks" comfy. Is your rear just not conditioned to riding yet? It may take time to toughen up.
If it were my bike I would put front brake on and ditch the rear, but whatever.
Ride the crap out of that thing!