Those are the stock supports and similar to Model A. I think C&G of Escondido Ca. repro them. Actually if you check their online catalogue they stock a lot of woodie related stuff. Good people to deal with. Check it out! I see you are still leaning toward an upper and lower tailgate. Actually the access to the rear area of a woodie is awkward thru the upper/lower tailgate configuration, ask the man who owns one! Reconsider making a hatch. Millions of minivans later it's the way to go but don't let me tell you what to do it's your baby...
Bill