While compiling a current list of existing trolleys or RR cars that were converted to diners (as in roadside food establishments), I stumbled on a wikipedia article on Chapel cars. These railroad chapels were built by various denominations to "spread the Word" by rail. To me, this was a previously unknown type of railroad car and it got me day-dreaming about a conversion project -- especially after following a recent post on different model options for churches on layouts. (For the space-challenged, this car seemed like a great find!)
Then, Lo and Behold! In my research, I found that an 1898 Barney & Smith chapel car was actually converted into a roadside diner and then eventually made its way to the Northeast Railway Museum in Washington state for restoration. Here's a link dedicated just to car #5, the Messinger of Peace:
http://www.messengerofpeace.org/A.php
One of the links on the left-hand side includes a floor plan and there are various stories about living and working in the car.
Enjoy,
Tomlinson Run Railroad
P.S. - Much more later on my diner-trolley-diner research. Hopefully, I can post something before grad school starts up again and I have to do "real" research again!