We know there have been a number of posts on this subject, but there seems to be as many solutions as there are Airstreams out there! So here is a link to our blog that shows how we solved the problem in a 1962 Flying Cloud. Having read as many of the previous posts as we could, we were able to glean hundreds of little nuggets and we came up with a stock 23 gal tank at a reasonable price that fit like a glove. As there also seems to be as many frame configurations as there are Airstreams as well, this will not work for everyone, but it is a good place to start. We were fortunate that the existing plumbing was relatively easy to modify to fit the new system. It is complete with shower and sink inlets, as well as an airgap to insure proper drainage. We hope this helps!
http://www.airforums.com/forums/blog...6-flyncld.html
FLYNCLD