This is a 4mm:1ft (OO-scale) chassis for my Southern Diagramme 3105 plastic-bodied (GRP) luggage van, British Rail PMV. This is improved over the other uploaded version, in that the vacuum cylinder is correctly central, how all the vans were built, rather than off at one end as the drawing I worked from showed it. Pick the print material you prefer in the trade-off between price and finish. Apart from the body, you will also require wheels on axles which are 26mm over pinpoints, chosen for your track gauge (e.g. OO/HO, EM or P4) and detailing parts, which are also available (footsteps, buffers, brake linkage safety loops, vacuum-actuated levers and brake linkages, brake handwheels, and brake blocks in pairs for each wheel (they fit from above, through holes in the floor). The body is also available, either as a single-piece, or separate sides/ends and roof. The chassis is LONGER than the body, because the van shock-absorbing by allowing limited sprung travel back and forth along the chassis. You will need to glue the body on centrally. You could try to mount it with some sort of spring and weight arrangement it to give a realistic shock-absorbing movement, but expectation should be managed.