Hello Rich, welcome to the forum. That's interesting about the dual condensers, I had not known that.
Here are some Passaic type links pulled together from past posts and other collections.

This is the cover of Ian Marshall's book of watercolors, Ironclads and Paddlers. There is an excellent narrative journal written by a sailor on the USS Nahant, here:
https://www.amazon.com/Monitor-Destruct ... 0872497615In the
Scientific American for December 12, 1863, on page 372, there is a long article entitled "The Monitors". This volume of the Scientific American (V9) can be downloaded as a pdf from Google Books. The article is dense with specifications and dimensions for the original USS Monitor and for the nine Passaic class monitors that followed it.
I was surprised to learn that the Czar built ten Passaic class monitors for the Russian navy, beginning in 1865, following the American plans. Presumeably this was under a licensing agreement from Ericsson.
https://en.m.wikipedia.org/wiki/Uragan-class_monitorRe the turret drive, I agree the V-twin engine was essentially the same as that of the original monitor. The drive configuration was quite different because, as you point out, the turrret axis was like a tree supporting the pilothouse, and the turret had to rotate around this fixed tree.
A diagram is posted here:
viewtopic.php?f=27&t=66949&start=40#p413439And here is a photo of the same general type of system aboard the Camanche:
download/file.php?id=35583&mode=viewThe reversing engine drives a crown gear that rotates in the plane of the lower deck, and is a little hard to see in this photo. It is geared to the vertical shaft at right, which ascends through the ceiling to drive the turret via a large diameter gear mounted below turret floor.
Finally, here is a link to Devin's expert model of the USS Weehawken:
http://www.devinjpoore.com/models/weehawken/index.htmbest, Michael