I'd be surprised to see one - ambulances tended to be on the lighter chassis based on cars, off the top of my head I can't think of any large lorries used as ambulances. Typical ambulances in British use were;
Ford Model T - http://www.flickr.com/photos/roblangham/2688405587/
And a number of American/Canadian built vehicles, I believe a mixture of Dodge/Chevrolets etc - http://www.flickr.com/photos/nlscotland/4699068067/ http://www.scarletfinders.co.uk/185.html
Thanks Rob. I thought so but I wanted to ask. I had seen a model of one someone built and I had never heard or seen a picture of one but I wanted to be sure.