5 plank, interesting... I thought they were 4 plank, or were they built (or rebuilt) as 4 plank?
The Cambrian C58 kit comes very close with a 5 plank body 70mm long, 32mm wide and 14mm high on a wooden solebar/drawbar.
The wheelbase is 36mm but looks extendable to 40mm as the solebar and W irons come on two different layers. The end stanchions can be trimmed to a taper with some cutters and 1mm x 1mm brass L section used to make the stanchions either side of the door. The two door springs can be formed from staples. With sides cut down to 2 plank the diagonal strapping stops just in the right place too.