Would be an interesting project and it is a van you really want so go for it, just be careful and don't warp the panels with all that welding. With the engine upgrades you've got planned and those luverley wheels it would be a real eye catcher. Maybe rather than try to re-create the original panels why not try a simpler method of a single sheet of metal to cover the window holes with a 'Woolfies Panels' logo painted on each side. That way it could easily be changed back to a camper should you fancy a change.
'Harvey the RV'