Thanks for the information, guys. I'll give the Mary Powell book a look and see what that has to offer.
Randy, that San Mateo has deck lines very close to the Hudson River ferries. The main difference is she's a screw steamer and the boats I'm looking into have side-wheel paddles, but for my purposes that might be close enough if I can fare that lower hull into the paper model I have.
I've been through Taubman's site from top to bottom and can't find any plans for such a boat. I am in the NYC area, so trip to the NY Historical Society might be in order.
Also the latest Ships in Scale has a great model of the side wheeler Chincoteague, a late 19th century ferry. It's not a double-ender, but the model looks darn close to what I want to pull off.
Thanks again, and any other suggestions, don't hesitate to shout (type) them out!