I've a book "Hint's, Tips & Gadgets for the Amateur Photographer" written in 1944 (UK) when photographic goods were in very short supply, it has an article on using older cameras & lenses as long focus lenses - essentially using a Leica body attached to the back of a plate camera.

These days body caps are cheap and cheerful and can be used to mount any SLR to a plate to fit a 5x4 or 9x12 camera.

Ian