The Caravanner never had a tub in the 50's and 60's. It was always a wet bath shower.
The Caravanner, Flying Cloud, Safari, Falcon and Custom 22 all shared the same platform. The only difference is where the windows and access doors were installed. The Caravanner was not as common as the Safari and FC.
I think your asking about the Fiberglass corner tub , vanity and they toliet mounted in the rear.
I would concentrate on roughtly 60-63 In 64 they started changing the shape a little and you might run into fitment problems. Much before 60 and the 22ft's didn't have a full width rear bathrooms in the 22ft coaches. Some of the larger coaches it did but the were a little larger then those used in the 22's and it's going to cause you issues with fitting in other interior cabinetry.
Be careful of the weight you add. You may need to also salvage a Hatch and install it into your coach to have access to some of the plumbing. Most rear baths had a rear hatch.
http://www.vintageairstream.com/archives/index.html
Good resource for you to see what things looked like in different years.