I don't know how much this would help you but if you Google Empress of Canada ship you will get a history and photos of the Mardi Gras, as when it first started operating in was built and operated as a trans-Atlantic liner and was named Empress of Canada. It had a sister ship called Empress of Britain, I think. However, the Empress of Canada was bought and refurbished with some paint and a shoestring and went on to become Carnival's first ship, the Mardi Gras.
I sailed it back in '83 but don't have the complete deck plans.
Hopefully this may help you a little.