Anything is possible… provided you’re prepared to pay for it. It would certainly be technically possible to convert a Sprinter van to dual rear wheels, but you’d need to source a rear axle that both mounted the dual wheels as well as being compatible with the van’s existing suspension and braking systems. Perhaps there’s a version of the Sprinter (perhaps sold overseas) that would be a donor for such a thing, but you might need to look further afield to find the bits and pieces necessary for the conversion.But even if you can physically make it all work, there’d be a significant cost in getting the modified vehicle re-engineered (and tested) to ensure that it was still safe to drive on public roads. Until then, the van would not legally be roadworthy. You might also find that your insurance company would take a fairly conservative view of such a conversion, too.I think you’d need to budget several thousand dollars for such a project. Assuming the conversion was to increase the van’s payload, you might find that simply buying a different vehicle with the payload you require might be the simpler, cheaper route. Also, a Sprinter converted to dual wheels might be more difficult to unload when it’s time to trade up to a new vehicle.