Wayne ..
That looks like a converted Naffi wagon..There is a restored one in the Canadian War museum ,even the paint on yours looks the same and is the original colour..
Sort of a light grey-white.
Here is an example of how they were built..but with different vehicles..
http://www.flickr.com/photos/john_64/4589855040/
The NAFFI body was probably replaced but could have been used buy the hospital and purchased from the military..The open backed body was probably used to replace the original NAFFI body..
Nice find and that would be an excellent way to restore it..That would be a winner at events..Pay for your trip..Sell tea and 'roo burgers out of it..
There is a picture of it..on this forum..go to the search function across the top header and type in MObile Canteen..
It is a Fordson,but many vehicles were converted.