This was posted in the are there 3 engine rooms in the TOS Enterprise? thread
Two engine rooms in the engineering hull, staggered, to fit in a 947' ship.
What was interesting about that thread is that the engine crew and Kirk in "The Immunity Syndrome" all were thrown towards the entrance of the room when the ship jerked forward. That would suggest that this particular room, with the EMM having a different console, was on the port side, with the entrance facing aft. For contrast, the bridge crew went to the back of the bridge in the same episode when accelerating forward.
What that also means is that the engine room is going to get more crowded by these big rooms quicker than I had planned