I think as Chris says, the actual body on a MWR is the same as MWD, the extra plank is bracketed to the canopy frame. We had a MWR in the yard once and it had all the earth links between metal cab panels, etc, but body was exactly the same as a MWD that I was restoring. Good timber is worth going for, nothing worse than sap bubbling paint work, shrinking planks, etc. You might find Whitworth coach bolts are some old established body builder or try searching on web.