The VOFX is built up from an AMK Engineering kit (with Steam Era Models bogies) and added detail - handrails, additional fine tarp rope railings, brake chain and motion, air hoses, tarp and card tarp supports, decals and Kadee #58 couplers. Other than that it's a pretty standard build of the kit. I have included some pictures below showing the progression of the build.
Showing the added tarp rope railings per several VOFXs seen on Shepparton-Scoones Siding (Kyabram) traffic in the late 1990s.
Showing card formers cut out to the shape of the "lower" style of tarp support gear.
Tarp formed and printed from PC drawing of same and weathered with wagon again in accordance of VOFX's seen in teh Shepparton area as mentioned above.